Baixar arquivo usando Javascript / jQuery

Eu tenho um requisito muito semelhante especificado aqui .

Eu preciso que o navegador do usuário inicie um download manualmente quando $('a#someID').click();

Mas não posso usar o window.hrefmétodo, pois ele substitui o conteúdo da página atual pelo arquivo que você está tentando baixar.

Em vez disso, quero abrir o download em uma nova janela / guia. Como isso é possível?

Use um invisível <iframe>:

<iframe id="my_iframe" style="display:none;"></iframe>
<script>
function Download(url) {
    document.getElementById('my_iframe').src = url;
};
</script>

Para forçar o navegador a baixar um arquivo que seria capaz de renderizar (como HTML ou arquivos de texto), é necessário que o servidor defina o Tipo MIME do arquivo como um valor sem sentido, como application/x-please-download-meou alternativamente application/octet-stream, usado para binários arbitrários dados.

Se você deseja abri-lo apenas em uma nova guia, a única maneira de fazer isso é o usuário clicar em um link com o targetatributo definido como _blank.

No jQuery:

$('a#someID').attr({target: '_blank', 
                    href  : 'http://localhost/directory/file.pdf'});

Sempre que esse link é clicado, ele baixa o arquivo em uma nova guia / janela.

Atualização dos navegadores modernos de 2019

Esta é a abordagem que eu recomendaria agora com algumas ressalvas:

• É necessário um navegador relativamente moderno
• Se o arquivo deve ser muito grande, você provavelmente deve fazer algo semelhante à abordagem original (iframe e cookie), porque algumas das operações abaixo provavelmente consumirão memória do sistema pelo menos tão grande quanto o arquivo que está sendo baixado e / ou outra CPU interessante efeitos colaterais.

fetch('https://jsonplaceholder.typicode.com/todos/1')
  .then(resp => resp.blob())
  .then(blob => {
    const url = window.URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.style.display = 'none';
    a.href = url;
    // the filename you want
    a.download = 'todo-1.json';
    document.body.appendChild(a);
    a.click();
    window.URL.revokeObjectURL(url);
    alert('your file has downloaded!'); // or you know, something with better UX...
  })
  .catch(() => alert('oh no!'));

2012 abordagem original baseada em jQuery / iframe / cookie

Eu criei o plugin jQuery File Download ( Demo ) ( GitHub ), que também pode ajudar com sua situação. Funciona da mesma forma com um iframe, mas possui alguns recursos interessantes que eu achei bastante úteis:

• Muito fácil de configurar com recursos visuais (jQuery UI Dialog, mas não obrigatório), tudo também é testado

• O usuário nunca sai da mesma página em que iniciou o download do arquivo. Esse recurso está se tornando crucial para aplicativos da web modernos

• As funções successCallback e failCallback permitem que você seja explícito sobre o que o usuário vê em qualquer situação

• Em conjunto com a interface do usuário do jQuery, um desenvolvedor pode mostrar facilmente um modal informando ao usuário que um download de arquivo está ocorrendo, dissolver o modal após o início do download ou até mesmo informar o usuário de uma maneira amigável de que ocorreu um erro. Veja a demonstração para um exemplo disso. Espero que isso ajude alguém!

Aqui está uma demonstração simples de caso de uso usando a fonte do plugin com promessas. A página de demonstração inclui muitos outros exemplos de 'melhor UX'.

$.fileDownload('some/file.pdf')
    .done(function () { alert('File download a success!'); })
    .fail(function () { alert('File download failed!'); });

function downloadURI(uri, name) 
{
    var link = document.createElement("a");
    // If you don't know the name or want to use
    // the webserver default set name = ''
    link.setAttribute('download', name);
    link.href = uri;
    document.body.appendChild(link);
    link.click();
    link.remove();
}

Verifique se o (s) seu (s) navegador (s) de destino executam o snippet acima sem problemas:
http://caniuse.com/#feat=download

Estou surpreso que muitas pessoas não conheçam o atributo de download de alguns elementos. Por favor, ajude a espalhar a palavra sobre isso! Você pode ter um link html oculto e fingir um clique nele. Se o link html tiver o atributo de download, ele fará o download do arquivo, não o exibirá, não importa o quê. Aqui está o código. Ele fará o download de uma foto de gato, se puder encontrá-la.

document.getElementById('download').click();

<a href="https://docs.google.com/uc?id=0B0jH18Lft7ypSmRjdWg1c082Y2M" download id="download" hidden></a>

Nota: Isso não é suportado em todos os navegadores: http://www.w3schools.com/tags/att_a_download.asp

Eu recomendo usar o downloadatributo para download em vez do jQuery:

<a href="your_link" download> file_name </a>

Isso fará o download do seu arquivo, sem abri-lo.

Se você já estiver usando o jQuery, poderá se aventurar para produzir um trecho menor.
Uma versão do jQuery da resposta de Andrew:

var $idown;  // Keep it outside of the function, so it's initialized once.
downloadURL : function(url) {
  if ($idown) {
    $idown.attr('src',url);
  } else {
    $idown = $('<iframe>', { id:'idown', src:url }).hide().appendTo('body');
  }
},
//... How to use it:
downloadURL('http://whatever.com/file.pdf');

Funciona no Chrome, Firefox e IE8 e superior.

var link=document.createElement('a');
document.body.appendChild(link);
link.href=url ;
link.click();

Exemplo simples usando um iframe

function downloadURL(url) {
    var hiddenIFrameID = 'hiddenDownloader',
        iframe = document.getElementById(hiddenIFrameID);
    if (iframe === null) {
        iframe = document.createElement('iframe');
        iframe.id = hiddenIFrameID;
        iframe.style.display = 'none';
        document.body.appendChild(iframe);
    }
    iframe.src = url;
};

Em seguida, basta chamar a função onde quiser:

downloadURL('path/to/my/file');

Isso pode ser útil se você não precisar navegar em outra página. Esta é a função javascript básica, portanto pode ser usada em qualquer plataforma em que o back-end esteja em Javascript.

window.location.assign('any url or file path')

Apenas sete anos depois, aqui vem uma solução jQuery de uma linha usando um formulário em vez de um iframe ou link:

$('<form></form>')
     .attr('action', filePath)
     .appendTo('body').submit().remove();

Eu testei isso em

• Chrome 55
• Firefox 50
• Edge IE8-10
• iOS 10 (Safari / Chrome)
• Android Chrome

Se alguém souber de alguma desvantagem com esta solução, ficarei muito feliz em saber sobre eles.

Demonstração completa:

<html>
<head><script src="https://code.jquery.com/jquery-1.11.3.js"></script></head>
<body>
<script>
    var filePath = window.prompt("Enter a file URL","http://jqueryui.com/resources/download/jquery-ui-1.12.1.zip");
    $('<form></form>').attr('action', filePath).appendTo('body').submit().remove();
</script>
</body>
</html>

Não sei se a pergunta é muito antiga, mas a configuração de window.location para um URL de download funcionará, desde que o tipo mime de download esteja correto (por exemplo, um arquivo zip).

var download = function(downloadURL) {

   location = downloadURL;

});

download('http://example.com/archive.zip'); //correct usage
download('http://example.com/page.html'); //DON'T

Acabei usando o trecho abaixo e funciona na maioria dos navegadores, mas não testado no IE.

let data = JSON.stringify([{email: "test@domain.com", name: "test"}, {email: "anothertest@example.com", name: "anothertest"}]);

let type = "application/json", name = "testfile.json";
downloader(data, type, name)

function downloader(data, type, name) {
	let blob = new Blob([data], {type});
	let url = window.URL.createObjectURL(blob);
	downloadURI(url, name);
	window.URL.revokeObjectURL(url);
}

function downloadURI(uri, name) {
    let link = document.createElement("a");
    link.download = name;
    link.href = uri;
    link.click();
}

Atualizar

function downloadURI(uri, name) {
    let link = document.createElement("a");
    link.download = name;
    link.href = uri;
    link.click();
}

function downloader(data, type, name) {
    let blob = new Blob([data], {type});
    let url = window.URL.createObjectURL(blob);
    downloadURI(url, name);
    window.URL.revokeObjectURL(url);
}

Para melhorar a resposta do Imagine Breaker, isso é suportado no FF & IE:

var evt = document.createEvent("MouseEvents");
evt.initMouseEvent("click", true, true, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);

function downloadURI(uri, name) {
    var link = document.createElement("a");
    link.download = name;
    link.href = uri;
    link.dispatchEvent(evt);
}

Em outras palavras, basta usar uma dispatchEventfunção em vez de click();

Talvez apenas o seu javascript abra uma página que apenas baixa um arquivo, como quando você arrasta um link de download para uma nova guia:

Window.open("https://www.MyServer.
Org/downloads/ardiuno/WgiWho=?:8080")

Com a janela aberta, abra uma página de download que fecha automaticamente.

O código mais completo e funcional (testado) para fazer o download de dados para o FireFox, o Chrome e o IE Code está a seguir. Suponha que os dados estão em texarea campo, que tem id = 'textarea_area' e filename é o nome do arquivo onde os dados serão transferidos.

function download(filename) {
    if (typeof filename==='undefined') filename = ""; // default
    value = document.getElementById('textarea_area').value;

    filetype="text/*";
    extension=filename.substring(filename.lastIndexOf("."));
    for (var i = 0; i < extToMIME.length; i++) {
        if (extToMIME[i][0].localeCompare(extension)==0) {
            filetype=extToMIME[i][1];
            break;
        }
    }


    var pom = document.createElement('a');
    pom.setAttribute('href', 'data: '+filetype+';charset=utf-8,' + '\ufeff' + encodeURIComponent(value)); // Added BOM too
    pom.setAttribute('download', filename);


    if (document.createEvent) {
        if (navigator.userAgent.indexOf('MSIE') !== -1 || navigator.appVersion.indexOf('Trident/') > 0) { // IE
            blobObject = new Blob(['\ufeff'+value]);
            window.navigator.msSaveBlob(blobObject, filename);
        } else { // FF, Chrome
            var event = document.createEvent('MouseEvents');
            event.initEvent('click', true, true);
            pom.dispatchEvent(event);
        }
    } else if( document.createEventObject ) { // Have No Idea
        var evObj = document.createEventObject();
        pom.fireEvent( 'onclick' , evObj );
    } else { // For Any Case
        pom.click();
    }

}

e depois é só ligar

<a href="javascript:download();">Download</a>

Para iniciar o download.

A matriz para definir o tipo MIME correto para a caixa de diálogo de download PODE SER o seguinte:

// ----------------------- Extensions to MIME --------- //

        // List of mime types
        // combination of values from Windows 7 Registry and 
        // from C:\Windows\System32\inetsrv\config\applicationHost.config
        // some added, including .7z and .dat
    var extToMIME = [
        [".323", "text/h323"],
        [".3g2", "video/3gpp2"],
        [".3gp", "video/3gpp"],
        [".3gp2", "video/3gpp2"],
        [".3gpp", "video/3gpp"],
        [".7z", "application/x-7z-compressed"],
        [".aa", "audio/audible"],
        [".AAC", "audio/aac"],
        [".aaf", "application/octet-stream"],
        [".aax", "audio/vnd.audible.aax"],
        [".ac3", "audio/ac3"],
        [".aca", "application/octet-stream"],
        [".accda", "application/msaccess.addin"],
        [".accdb", "application/msaccess"],
        [".accdc", "application/msaccess.cab"],
        [".accde", "application/msaccess"],
        [".accdr", "application/msaccess.runtime"],
        [".accdt", "application/msaccess"],
        [".accdw", "application/msaccess.webapplication"],
        [".accft", "application/msaccess.ftemplate"],
        [".acx", "application/internet-property-stream"],
        [".AddIn", "text/xml"],
        [".ade", "application/msaccess"],
        [".adobebridge", "application/x-bridge-url"],
        [".adp", "application/msaccess"],
        [".ADT", "audio/vnd.dlna.adts"],
        [".ADTS", "audio/aac"],
        [".afm", "application/octet-stream"],
        [".ai", "application/postscript"],
        [".aif", "audio/x-aiff"],
        [".aifc", "audio/aiff"],
        [".aiff", "audio/aiff"],
        [".air", "application/vnd.adobe.air-application-installer-package+zip"],
        [".amc", "application/x-mpeg"],
        [".application", "application/x-ms-application"],
        [".art", "image/x-jg"],
        [".asa", "application/xml"],
        [".asax", "application/xml"],
        [".ascx", "application/xml"],
        [".asd", "application/octet-stream"],
        [".asf", "video/x-ms-asf"],
        [".ashx", "application/xml"],
        [".asi", "application/octet-stream"],
        [".asm", "text/plain"],
        [".asmx", "application/xml"],
        [".aspx", "application/xml"],
        [".asr", "video/x-ms-asf"],
        [".asx", "video/x-ms-asf"],
        [".atom", "application/atom+xml"],
        [".au", "audio/basic"],
        [".avi", "video/x-msvideo"],
        [".axs", "application/olescript"],
        [".bas", "text/plain"],
        [".bcpio", "application/x-bcpio"],
        [".bin", "application/octet-stream"],
        [".bmp", "image/bmp"],
        [".c", "text/plain"],
        [".cab", "application/octet-stream"],
        [".caf", "audio/x-caf"],
        [".calx", "application/vnd.ms-office.calx"],
        [".cat", "application/vnd.ms-pki.seccat"],
        [".cc", "text/plain"],
        [".cd", "text/plain"],
        [".cdda", "audio/aiff"],
        [".cdf", "application/x-cdf"],
        [".cer", "application/x-x509-ca-cert"],
        [".chm", "application/octet-stream"],
        [".class", "application/x-java-applet"],
        [".clp", "application/x-msclip"],
        [".cmx", "image/x-cmx"],
        [".cnf", "text/plain"],
        [".cod", "image/cis-cod"],
        [".config", "application/xml"],
        [".contact", "text/x-ms-contact"],
        [".coverage", "application/xml"],
        [".cpio", "application/x-cpio"],
        [".cpp", "text/plain"],
        [".crd", "application/x-mscardfile"],
        [".crl", "application/pkix-crl"],
        [".crt", "application/x-x509-ca-cert"],
        [".cs", "text/plain"],
        [".csdproj", "text/plain"],
        [".csh", "application/x-csh"],
        [".csproj", "text/plain"],
        [".css", "text/css"],
        [".csv", "text/csv"],
        [".cur", "application/octet-stream"],
        [".cxx", "text/plain"],
        [".dat", "application/octet-stream"],
        [".datasource", "application/xml"],
        [".dbproj", "text/plain"],
        [".dcr", "application/x-director"],
        [".def", "text/plain"],
        [".deploy", "application/octet-stream"],
        [".der", "application/x-x509-ca-cert"],
        [".dgml", "application/xml"],
        [".dib", "image/bmp"],
        [".dif", "video/x-dv"],
        [".dir", "application/x-director"],
        [".disco", "text/xml"],
        [".dll", "application/x-msdownload"],
        [".dll.config", "text/xml"],
        [".dlm", "text/dlm"],
        [".doc", "application/msword"],
        [".docm", "application/vnd.ms-word.document.macroEnabled.12"],
        [".docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"],
        [".dot", "application/msword"],
        [".dotm", "application/vnd.ms-word.template.macroEnabled.12"],
        [".dotx", "application/vnd.openxmlformats-officedocument.wordprocessingml.template"],
        [".dsp", "application/octet-stream"],
        [".dsw", "text/plain"],
        [".dtd", "text/xml"],
        [".dtsConfig", "text/xml"],
        [".dv", "video/x-dv"],
        [".dvi", "application/x-dvi"],
        [".dwf", "drawing/x-dwf"],
        [".dwp", "application/octet-stream"],
        [".dxr", "application/x-director"],
        [".eml", "message/rfc822"],
        [".emz", "application/octet-stream"],
        [".eot", "application/octet-stream"],
        [".eps", "application/postscript"],
        [".etl", "application/etl"],
        [".etx", "text/x-setext"],
        [".evy", "application/envoy"],
        [".exe", "application/octet-stream"],
        [".exe.config", "text/xml"],
        [".fdf", "application/vnd.fdf"],
        [".fif", "application/fractals"],
        [".filters", "Application/xml"],
        [".fla", "application/octet-stream"],
        [".flr", "x-world/x-vrml"],
        [".flv", "video/x-flv"],
        [".fsscript", "application/fsharp-script"],
        [".fsx", "application/fsharp-script"],
        [".generictest", "application/xml"],
        [".gif", "image/gif"],
        [".group", "text/x-ms-group"],
        [".gsm", "audio/x-gsm"],
        [".gtar", "application/x-gtar"],
        [".gz", "application/x-gzip"],
        [".h", "text/plain"],
        [".hdf", "application/x-hdf"],
        [".hdml", "text/x-hdml"],
        [".hhc", "application/x-oleobject"],
        [".hhk", "application/octet-stream"],
        [".hhp", "application/octet-stream"],
        [".hlp", "application/winhlp"],
        [".hpp", "text/plain"],
        [".hqx", "application/mac-binhex40"],
        [".hta", "application/hta"],
        [".htc", "text/x-component"],
        [".htm", "text/html"],
        [".html", "text/html"],
        [".htt", "text/webviewhtml"],
        [".hxa", "application/xml"],
        [".hxc", "application/xml"],
        [".hxd", "application/octet-stream"],
        [".hxe", "application/xml"],
        [".hxf", "application/xml"],
        [".hxh", "application/octet-stream"],
        [".hxi", "application/octet-stream"],
        [".hxk", "application/xml"],
        [".hxq", "application/octet-stream"],
        [".hxr", "application/octet-stream"],
        [".hxs", "application/octet-stream"],
        [".hxt", "text/html"],
        [".hxv", "application/xml"],
        [".hxw", "application/octet-stream"],
        [".hxx", "text/plain"],
        [".i", "text/plain"],
        [".ico", "image/x-icon"],
        [".ics", "application/octet-stream"],
        [".idl", "text/plain"],
        [".ief", "image/ief"],
        [".iii", "application/x-iphone"],
        [".inc", "text/plain"],
        [".inf", "application/octet-stream"],
        [".inl", "text/plain"],
        [".ins", "application/x-internet-signup"],
        [".ipa", "application/x-itunes-ipa"],
        [".ipg", "application/x-itunes-ipg"],
        [".ipproj", "text/plain"],
        [".ipsw", "application/x-itunes-ipsw"],
        [".iqy", "text/x-ms-iqy"],
        [".isp", "application/x-internet-signup"],
        [".ite", "application/x-itunes-ite"],
        [".itlp", "application/x-itunes-itlp"],
        [".itms", "application/x-itunes-itms"],
        [".itpc", "application/x-itunes-itpc"],
        [".IVF", "video/x-ivf"],
        [".jar", "application/java-archive"],
        [".java", "application/octet-stream"],
        [".jck", "application/liquidmotion"],
        [".jcz", "application/liquidmotion"],
        [".jfif", "image/pjpeg"],
        [".jnlp", "application/x-java-jnlp-file"],
        [".jpb", "application/octet-stream"],
        [".jpe", "image/jpeg"],
        [".jpeg", "image/jpeg"],
        [".jpg", "image/jpeg"],
        [".js", "application/x-javascript"],
        [".json", "application/json"],
        [".jsx", "text/jscript"],
        [".jsxbin", "text/plain"],
        [".latex", "application/x-latex"],
        [".library-ms", "application/windows-library+xml"],
        [".lit", "application/x-ms-reader"],
        [".loadtest", "application/xml"],
        [".lpk", "application/octet-stream"],
        [".lsf", "video/x-la-asf"],
        [".lst", "text/plain"],
        [".lsx", "video/x-la-asf"],
        [".lzh", "application/octet-stream"],
        [".m13", "application/x-msmediaview"],
        [".m14", "application/x-msmediaview"],
        [".m1v", "video/mpeg"],
        [".m2t", "video/vnd.dlna.mpeg-tts"],
        [".m2ts", "video/vnd.dlna.mpeg-tts"],
        [".m2v", "video/mpeg"],
        [".m3u", "audio/x-mpegurl"],
        [".m3u8", "audio/x-mpegurl"],
        [".m4a", "audio/m4a"],
        [".m4b", "audio/m4b"],
        [".m4p", "audio/m4p"],
        [".m4r", "audio/x-m4r"],
        [".m4v", "video/x-m4v"],
        [".mac", "image/x-macpaint"],
        [".mak", "text/plain"],
        [".man", "application/x-troff-man"],
        [".manifest", "application/x-ms-manifest"],
        [".map", "text/plain"],
        [".master", "application/xml"],
        [".mda", "application/msaccess"],
        [".mdb", "application/x-msaccess"],
        [".mde", "application/msaccess"],
        [".mdp", "application/octet-stream"],
        [".me", "application/x-troff-me"],
        [".mfp", "application/x-shockwave-flash"],
        [".mht", "message/rfc822"],
        [".mhtml", "message/rfc822"],
        [".mid", "audio/mid"],
        [".midi", "audio/mid"],
        [".mix", "application/octet-stream"],
        [".mk", "text/plain"],
        [".mmf", "application/x-smaf"],
        [".mno", "text/xml"],
        [".mny", "application/x-msmoney"],
        [".mod", "video/mpeg"],
        [".mov", "video/quicktime"],
        [".movie", "video/x-sgi-movie"],
        [".mp2", "video/mpeg"],
        [".mp2v", "video/mpeg"],
        [".mp3", "audio/mpeg"],
        [".mp4", "video/mp4"],
        [".mp4v", "video/mp4"],
        [".mpa", "video/mpeg"],
        [".mpe", "video/mpeg"],
        [".mpeg", "video/mpeg"],
        [".mpf", "application/vnd.ms-mediapackage"],
        [".mpg", "video/mpeg"],
        [".mpp", "application/vnd.ms-project"],
        [".mpv2", "video/mpeg"],
        [".mqv", "video/quicktime"],
        [".ms", "application/x-troff-ms"],
        [".msi", "application/octet-stream"],
        [".mso", "application/octet-stream"],
        [".mts", "video/vnd.dlna.mpeg-tts"],
        [".mtx", "application/xml"],
        [".mvb", "application/x-msmediaview"],
        [".mvc", "application/x-miva-compiled"],
        [".mxp", "application/x-mmxp"],
        [".nc", "application/x-netcdf"],
        [".nsc", "video/x-ms-asf"],
        [".nws", "message/rfc822"],
        [".ocx", "application/octet-stream"],
        [".oda", "application/oda"],
        [".odc", "text/x-ms-odc"],
        [".odh", "text/plain"],
        [".odl", "text/plain"],
        [".odp", "application/vnd.oasis.opendocument.presentation"],
        [".ods", "application/oleobject"],
        [".odt", "application/vnd.oasis.opendocument.text"],
        [".one", "application/onenote"],
        [".onea", "application/onenote"],
        [".onepkg", "application/onenote"],
        [".onetmp", "application/onenote"],
        [".onetoc", "application/onenote"],
        [".onetoc2", "application/onenote"],
        [".orderedtest", "application/xml"],
        [".osdx", "application/opensearchdescription+xml"],
        [".p10", "application/pkcs10"],
        [".p12", "application/x-pkcs12"],
        [".p7b", "application/x-pkcs7-certificates"],
        [".p7c", "application/pkcs7-mime"],
        [".p7m", "application/pkcs7-mime"],
        [".p7r", "application/x-pkcs7-certreqresp"],
        [".p7s", "application/pkcs7-signature"],
        [".pbm", "image/x-portable-bitmap"],
        [".pcast", "application/x-podcast"],
        [".pct", "image/pict"],
        [".pcx", "application/octet-stream"],
        [".pcz", "application/octet-stream"],
        [".pdf", "application/pdf"],
        [".pfb", "application/octet-stream"],
        [".pfm", "application/octet-stream"],
        [".pfx", "application/x-pkcs12"],
        [".pgm", "image/x-portable-graymap"],
        [".pic", "image/pict"],
        [".pict", "image/pict"],
        [".pkgdef", "text/plain"],
        [".pkgundef", "text/plain"],
        [".pko", "application/vnd.ms-pki.pko"],
        [".pls", "audio/scpls"],
        [".pma", "application/x-perfmon"],
        [".pmc", "application/x-perfmon"],
        [".pml", "application/x-perfmon"],
        [".pmr", "application/x-perfmon"],
        [".pmw", "application/x-perfmon"],
        [".png", "image/png"],
        [".pnm", "image/x-portable-anymap"],
        [".pnt", "image/x-macpaint"],
        [".pntg", "image/x-macpaint"],
        [".pnz", "image/png"],
        [".pot", "application/vnd.ms-powerpoint"],
        [".potm", "application/vnd.ms-powerpoint.template.macroEnabled.12"],
        [".potx", "application/vnd.openxmlformats-officedocument.presentationml.template"],
        [".ppa", "application/vnd.ms-powerpoint"],
        [".ppam", "application/vnd.ms-powerpoint.addin.macroEnabled.12"],
        [".ppm", "image/x-portable-pixmap"],
        [".pps", "application/vnd.ms-powerpoint"],
        [".ppsm", "application/vnd.ms-powerpoint.slideshow.macroEnabled.12"],
        [".ppsx", "application/vnd.openxmlformats-officedocument.presentationml.slideshow"],
        [".ppt", "application/vnd.ms-powerpoint"],
        [".pptm", "application/vnd.ms-powerpoint.presentation.macroEnabled.12"],
        [".pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation"],
        [".prf", "application/pics-rules"],
        [".prm", "application/octet-stream"],
        [".prx", "application/octet-stream"],
        [".ps", "application/postscript"],
        [".psc1", "application/PowerShell"],
        [".psd", "application/octet-stream"],
        [".psess", "application/xml"],
        [".psm", "application/octet-stream"],
        [".psp", "application/octet-stream"],
        [".pub", "application/x-mspublisher"],
        [".pwz", "application/vnd.ms-powerpoint"],
        [".qht", "text/x-html-insertion"],
        [".qhtm", "text/x-html-insertion"],
        [".qt", "video/quicktime"],
        [".qti", "image/x-quicktime"],
        [".qtif", "image/x-quicktime"],
        [".qtl", "application/x-quicktimeplayer"],
        [".qxd", "application/octet-stream"],
        [".ra", "audio/x-pn-realaudio"],
        [".ram", "audio/x-pn-realaudio"],
        [".rar", "application/octet-stream"],
        [".ras", "image/x-cmu-raster"],
        [".rat", "application/rat-file"],
        [".rc", "text/plain"],
        [".rc2", "text/plain"],
        [".rct", "text/plain"],
        [".rdlc", "application/xml"],
        [".resx", "application/xml"],
        [".rf", "image/vnd.rn-realflash"],
        [".rgb", "image/x-rgb"],
        [".rgs", "text/plain"],
        [".rm", "application/vnd.rn-realmedia"],
        [".rmi", "audio/mid"],
        [".rmp", "application/vnd.rn-rn_music_package"],
        [".roff", "application/x-troff"],
        [".rpm", "audio/x-pn-realaudio-plugin"],
        [".rqy", "text/x-ms-rqy"],
        [".rtf", "application/rtf"],
        [".rtx", "text/richtext"],
        [".ruleset", "application/xml"],
        [".s", "text/plain"],
        [".safariextz", "application/x-safari-safariextz"],
        [".scd", "application/x-msschedule"],
        [".sct", "text/scriptlet"],
        [".sd2", "audio/x-sd2"],
        [".sdp", "application/sdp"],
        [".sea", "application/octet-stream"],
        [".searchConnector-ms", "application/windows-search-connector+xml"],
        [".setpay", "application/set-payment-initiation"],
        [".setreg", "application/set-registration-initiation"],
        [".settings", "application/xml"],
        [".sgimb", "application/x-sgimb"],
        [".sgml", "text/sgml"],
        [".sh", "application/x-sh"],
        [".shar", "application/x-shar"],
        [".shtml", "text/html"],
        [".sit", "application/x-stuffit"],
        [".sitemap", "application/xml"],
        [".skin", "application/xml"],
        [".sldm", "application/vnd.ms-powerpoint.slide.macroEnabled.12"],
        [".sldx", "application/vnd.openxmlformats-officedocument.presentationml.slide"],
        [".slk", "application/vnd.ms-excel"],
        [".sln", "text/plain"],
        [".slupkg-ms", "application/x-ms-license"],
        [".smd", "audio/x-smd"],
        [".smi", "application/octet-stream"],
        [".smx", "audio/x-smd"],
        [".smz", "audio/x-smd"],
        [".snd", "audio/basic"],
        [".snippet", "application/xml"],
        [".snp", "application/octet-stream"],
        [".sol", "text/plain"],
        [".sor", "text/plain"],
        [".spc", "application/x-pkcs7-certificates"],
        [".spl", "application/futuresplash"],
        [".src", "application/x-wais-source"],
        [".srf", "text/plain"],
        [".SSISDeploymentManifest", "text/xml"],
        [".ssm", "application/streamingmedia"],
        [".sst", "application/vnd.ms-pki.certstore"],
        [".stl", "application/vnd.ms-pki.stl"],
        [".sv4cpio", "application/x-sv4cpio"],
        [".sv4crc", "application/x-sv4crc"],
        [".svc", "application/xml"],
        [".swf", "application/x-shockwave-flash"],
        [".t", "application/x-troff"],
        [".tar", "application/x-tar"],
        [".tcl", "application/x-tcl"],
        [".testrunconfig", "application/xml"],
        [".testsettings", "application/xml"],
        [".tex", "application/x-tex"],
        [".texi", "application/x-texinfo"],
        [".texinfo", "application/x-texinfo"],
        [".tgz", "application/x-compressed"],
        [".thmx", "application/vnd.ms-officetheme"],
        [".thn", "application/octet-stream"],
        [".tif", "image/tiff"],
        [".tiff", "image/tiff"],
        [".tlh", "text/plain"],
        [".tli", "text/plain"],
        [".toc", "application/octet-stream"],
        [".tr", "application/x-troff"],
        [".trm", "application/x-msterminal"],
        [".trx", "application/xml"],
        [".ts", "video/vnd.dlna.mpeg-tts"],
        [".tsv", "text/tab-separated-values"],
        [".ttf", "application/octet-stream"],
        [".tts", "video/vnd.dlna.mpeg-tts"],
        [".txt", "text/plain"],
        [".u32", "application/octet-stream"],
        [".uls", "text/iuls"],
        [".user", "text/plain"],
        [".ustar", "application/x-ustar"],
        [".vb", "text/plain"],
        [".vbdproj", "text/plain"],
        [".vbk", "video/mpeg"],
        [".vbproj", "text/plain"],
        [".vbs", "text/vbscript"],
        [".vcf", "text/x-vcard"],
        [".vcproj", "Application/xml"],
        [".vcs", "text/plain"],
        [".vcxproj", "Application/xml"],
        [".vddproj", "text/plain"],
        [".vdp", "text/plain"],
        [".vdproj", "text/plain"],
        [".vdx", "application/vnd.ms-visio.viewer"],
        [".vml", "text/xml"],
        [".vscontent", "application/xml"],
        [".vsct", "text/xml"],
        [".vsd", "application/vnd.visio"],
        [".vsi", "application/ms-vsi"],
        [".vsix", "application/vsix"],
        [".vsixlangpack", "text/xml"],
        [".vsixmanifest", "text/xml"],
        [".vsmdi", "application/xml"],
        [".vspscc", "text/plain"],
        [".vss", "application/vnd.visio"],
        [".vsscc", "text/plain"],
        [".vssettings", "text/xml"],
        [".vssscc", "text/plain"],
        [".vst", "application/vnd.visio"],
        [".vstemplate", "text/xml"],
        [".vsto", "application/x-ms-vsto"],
        [".vsw", "application/vnd.visio"],
        [".vsx", "application/vnd.visio"],
        [".vtx", "application/vnd.visio"],
        [".wav", "audio/wav"],
        [".wave", "audio/wav"],
        [".wax", "audio/x-ms-wax"],
        [".wbk", "application/msword"],
        [".wbmp", "image/vnd.wap.wbmp"],
        [".wcm", "application/vnd.ms-works"],
        [".wdb", "application/vnd.ms-works"],
        [".wdp", "image/vnd.ms-photo"],
        [".webarchive", "application/x-safari-webarchive"],
        [".webtest", "application/xml"],
        [".wiq", "application/xml"],
        [".wiz", "application/msword"],
        [".wks", "application/vnd.ms-works"],
        [".WLMP", "application/wlmoviemaker"],
        [".wlpginstall", "application/x-wlpg-detect"],
        [".wlpginstall3", "application/x-wlpg3-detect"],
        [".wm", "video/x-ms-wm"],
        [".wma", "audio/x-ms-wma"],
        [".wmd", "application/x-ms-wmd"],
        [".wmf", "application/x-msmetafile"],
        [".wml", "text/vnd.wap.wml"],
        [".wmlc", "application/vnd.wap.wmlc"],
        [".wmls", "text/vnd.wap.wmlscript"],
        [".wmlsc", "application/vnd.wap.wmlscriptc"],
        [".wmp", "video/x-ms-wmp"],
        [".wmv", "video/x-ms-wmv"],
        [".wmx", "video/x-ms-wmx"],
        [".wmz", "application/x-ms-wmz"],
        [".wpl", "application/vnd.ms-wpl"],
        [".wps", "application/vnd.ms-works"],
        [".wri", "application/x-mswrite"],
        [".wrl", "x-world/x-vrml"],
        [".wrz", "x-world/x-vrml"],
        [".wsc", "text/scriptlet"],
        [".wsdl", "text/xml"],
        [".wvx", "video/x-ms-wvx"],
        [".x", "application/directx"],
        [".xaf", "x-world/x-vrml"],
        [".xaml", "application/xaml+xml"],
        [".xap", "application/x-silverlight-app"],
        [".xbap", "application/x-ms-xbap"],
        [".xbm", "image/x-xbitmap"],
        [".xdr", "text/plain"],
        [".xht", "application/xhtml+xml"],
        [".xhtml", "application/xhtml+xml"],
        [".xla", "application/vnd.ms-excel"],
        [".xlam", "application/vnd.ms-excel.addin.macroEnabled.12"],
        [".xlc", "application/vnd.ms-excel"],
        [".xld", "application/vnd.ms-excel"],
        [".xlk", "application/vnd.ms-excel"],
        [".xll", "application/vnd.ms-excel"],
        [".xlm", "application/vnd.ms-excel"],
        [".xls", "application/vnd.ms-excel"],
        [".xlsb", "application/vnd.ms-excel.sheet.binary.macroEnabled.12"],
        [".xlsm", "application/vnd.ms-excel.sheet.macroEnabled.12"],
        [".xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"],
        [".xlt", "application/vnd.ms-excel"],
        [".xltm", "application/vnd.ms-excel.template.macroEnabled.12"],
        [".xltx", "application/vnd.openxmlformats-officedocument.spreadsheetml.template"],
        [".xlw", "application/vnd.ms-excel"],
        [".xml", "text/xml"],
        [".xmta", "application/xml"],
        [".xof", "x-world/x-vrml"],
        [".XOML", "text/plain"],
        [".xpm", "image/x-xpixmap"],
        [".xps", "application/vnd.ms-xpsdocument"],
        [".xrm-ms", "text/xml"],
        [".xsc", "application/xml"],
        [".xsd", "text/xml"],
        [".xsf", "text/xml"],
        [".xsl", "text/xml"],
        [".xslt", "text/xml"],
        [".xsn", "application/octet-stream"],
        [".xss", "application/xml"],
        [".xtp", "application/octet-stream"],
        [".xwd", "image/x-xwindowdump"],
        [".z", "application/x-compress"],
        [".zip", "application/x-zip-compressed"]
];

// ----------------------- End of Extensions to MIME --------- //

para mim isso está funcionando ok testado no chrome v72

function down_file(url,name){
var a = $("<a>")
    .attr("href", url)
    .attr("download", name)
    .appendTo("body");
a[0].click();
a.remove();
}

down_file('https://www.useotools.com/uploads/nulogo[1].png','logo.png')

Eu tive bons resultados com o uso de uma tag FORM, pois ela funciona em qualquer lugar e você não precisa criar arquivos temporariamente no servidor. O método funciona assim.

No lado do cliente (página HTML), você cria um formulário invisível como este

<form method="POST" action="/download.php" target="_blank" id="downloadForm">
    <input type="hidden" name="data" id="csv">
</form>

Então você adiciona este código Javascript ao seu botão:

$('#button').click(function() {
     $('#csv').val('---your data---');
     $('#downloadForm').submit();
}

No lado do servidor, você tem o seguinte código PHP em download.php:

<?php
header('Content-Type: text/csv');
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename=out.csv');
header('Content-Transfer-Encoding: binary');
header('Connection: Keep-Alive');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . strlen($data));

echo $_REQUEST['data'];
exit();

Você pode até criar arquivos zip dos seus dados assim:

<?php

$file = tempnam("tmp", "zip");

$zip = new ZipArchive();
$zip->open($file, ZipArchive::OVERWRITE);
$zip->addFromString('test.csv', $_REQUEST['data']);
$zip->close();

header('Content-Type: application/zip');
header('Content-Length: ' . filesize($file));
header('Content-Disposition: attachment; filename="file.zip"');
readfile($file);
unlink($file); 

A melhor parte é que não deixa nenhum arquivo residual no seu servidor, pois tudo é criado e destruído em tempo real!

A resposta enviada por hitesh em 30 de dezembro de 13 funciona de fato. Requer apenas um pequeno ajuste:

O arquivo PHP pode se chamar. Em outras palavras, basta criar um arquivo chamado saveAs.php e colocar esse código nele ...

        <a href="saveAs.php?file_source=YourDataFile.pdf">Download pdf here</a>

    <?php
        if (isset($_GET['file_source'])) {
            $fullPath = $_GET['file_source'];
            if($fullPath) {
                $fsize = filesize($fullPath);
                $path_parts = pathinfo($fullPath);
                $ext = strtolower($path_parts["extension"]);
                switch ($ext) {
                    case "pdf":
                    header("Content-Disposition: attachment; filename=\"".$path_parts["basename"]."\""); // use 'attachment' to force a download
                    header("Content-type: application/pdf"); // add here more headers for diff. extensions
                    break;
                    default;
                    header("Content-type: application/octet-stream");
                    header("Content-Disposition: filename=\"".$path_parts["basename"]."\"");
                }
                if($fsize) {//checking if file size exist
                  header("Content-length: $fsize");
                }
                readfile($fullPath);
                exit;
            }
        }
    ?>

Essas funções são usadas no stacktrace.js :

/**
 * Try XHR methods in order and store XHR factory.
 *
 * @return <Function> XHR function or equivalent
 */
var createXMLHTTPObject = function() {
    var xmlhttp, XMLHttpFactories = [
        function() {
            return new XMLHttpRequest();
        }, function() {
            return new ActiveXObject('Msxml2.XMLHTTP');
        }, function() {
            return new ActiveXObject('Msxml3.XMLHTTP');
        }, function() {
            return new ActiveXObject('Microsoft.XMLHTTP');
        }
    ];
    for (var i = 0; i < XMLHttpFactories.length; i++) {
        try {
            xmlhttp = XMLHttpFactories[i]();
            // Use memoization to cache the factory
            createXMLHTTPObject = XMLHttpFactories[i];
            return xmlhttp;
        } catch (e) {
        }
    }
}

/**
 * @return the text from a given URL
 */
function ajax(url) {
    var req = createXMLHTTPObject();
    if (req) {
        try {
            req.open('GET', url, false);
            req.send(null);
            return req.responseText;
        } catch (e) {
        }
    }
    return '';
}

Eu sugiro que você use o evento mousedown, chamado ANTES do evento click. Dessa forma, o navegador manipula o evento click naturalmente, o que evita qualquer estranheza no código:

(function ($) {


    // with this solution, the browser handles the download link naturally (tested in chrome and firefox)
    $(document).ready(function () {

        var url = '/private/downloads/myfile123.pdf';
        $("a#someID").on('mousedown', function () {
            $(this).attr("href", url);
        });

    });
})(jQuery);

Excelente solução da Corbacho, acabei de me adaptar para me livrar da var

function downloadURL(url) {
    if( $('#idown').length ){
        $('#idown').attr('src',url);
    }else{
        $('<iframe>', { id:'idown', src:url }).hide().appendTo('body');
    }
}

Firefox e Chrome testados:

var link = document.createElement('a');
link.download = 'fileName.ext'
link.href = 'http://down.serv/file.ext';

// Because firefox not executing the .click() well
// We need to create mouse event initialization.
var clickEvent = document.createEvent("MouseEvent");
clickEvent.initEvent("click", true, true);

link.dispatchEvent(clickEvent);

Esta é realmente a solução "chrome" para o firefox (não a testei em outros navegadores, por favor, deixe comentários sobre a compilabilidade)

Há muitas pequenas coisas que podem acontecer ao tentar baixar um arquivo. A inconsistência entre navegadores é um pesadelo. Acabei usando esta ótima pequena biblioteca. https://github.com/rndme/download

O interessante é que ele é flexível não apenas para os URLs, mas também para os dados do lado do cliente que você deseja baixar.

1. sequência de texto
2. dataURL de texto
3. blob de texto
4. matrizes de texto
5. string html
6. blob html
7. retorno de chamada ajax
8. arquivos binários

Usando tag de âncora e PHP, isso pode ser feito, verifique esta resposta

Chamada do JQuery Ajax para download de arquivo PDF

HTML
    <a href="www.example.com/download_file.php?file_source=example.pdf">Download pdf here</a>

PHP
<?php
$fullPath = $_GET['fileSource'];
if($fullPath) {
    $fsize = filesize($fullPath);
    $path_parts = pathinfo($fullPath);
    $ext = strtolower($path_parts["extension"]);
    switch ($ext) {
        case "pdf":
        header("Content-Disposition: attachment; filename=\"".$path_parts["basename"]."\""); // use 'attachment' to force a download
        header("Content-type: application/pdf"); // add here more headers for diff. extensions
        break;
        default;
        header("Content-type: application/octet-stream");
        header("Content-Disposition: filename=\"".$path_parts["basename"]."\"");
    }
    if($fsize) {//checking if file size exist
      header("Content-length: $fsize");
    }
    readfile($fullPath);
    exit;
}
?>

Estou verificando o tamanho do arquivo, porque se você carregar pdf do CDN cloudfront, não obterá o tamanho do documento que força o download do documento em 0kb. Para evitar isso, estou verificando esta condição

 if($fsize) {//checking if file size exist
      header("Content-length: $fsize");
    }

Sei que estou atrasado para a festa, mas gostaria de compartilhar minha solução, que é a variação da solução Imagine Breaker acima. Tentei usar a solução dele, porque a solução dele parece mais simples e fácil para mim. Mas, como já foi dito, não funcionou em alguns navegadores, então fiz algumas variações usando o jquery.

Espero que isso possa ajudar alguém lá fora.

function download(url) {
  var link = document.createElement("a");
  $(link).click(function(e) {
    e.preventDefault();
    window.location.href = url;
  });
  $(link).click();
}

Nota: Não suportado em todos os navegadores.

Eu estava procurando uma maneira de baixar um arquivo usando o jquery sem precisar definir o URL do arquivo no atributo href desde o início.

jQuery('<a/>', {
    id: 'downloadFile',
    href: 'http://cdn.sstatic.net/Sites/stackoverflow/img/apple-touch-icon@2.png',
    style: 'display:hidden;',
    download: ''
}).appendTo('body');

$("#downloadFile")[0].click();

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

Eu uso a solução da @ rakaloof sem JQuery (porque você não precisa dela aqui ). Obrigado pela idéia! Aqui está uma solução baseada em formulário vanillaJS:

const uri = 'https://upload.wikimedia.org/wikipedia/commons/b/bb/Test_ogg_mp3_48kbps.wav';
let form = document.createElement("form");
form.setAttribute('action', uri);
document.body.appendChild(form);
form.submit();
document.body.removeChild(document.body.lastElementChild);