How to download file with javascript?

since the answer from @saibbyweb does not work in all browsers as I write this, i recommend an other but similar solution, tested and working in latest (as of writing) Firefox, Chrome, Opera, Edge, Safari, mobile Safari, mobile Chrome:

function downloadUrl(url){
    window.open(url, '_self');
}

Needless to say you could also open links in new Tabs with _blank instead of _self, but you potentially startle Popup-Blockers by opening new tabs/windows with Javascript.

You can provide the link to this function to download the file :

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