Using HTML5/JavaScript to generate and save a file

Question

I've been fiddling with WebGL lately, and have gotten a Collada reader working. Problem is it's pretty slow (Collada is a very verbose format), so I'm going to start converting files to a easier to use format (probably JSON). I already have the code to parse the file in JavaScript, so I may as well use it as my exporter too! The problem is saving.

Now, I know that I can parse the file, send the result to the server, and have the browser request the file back from the server as a download. But in reality the server has nothing to do with this particular process, so why get it involved? I already have the contents of the desired file in memory. Is there any way that I could present the user with a download using pure JavaScript? (I doubt it, but might as well ask...)

And to be clear: I am not trying to access the filesystem without the users knowledge! The user will provide a file (probably via drag and drop), the script will transform the file in memory, and the user will be prompted to download the result. All of which should be "safe" activities as far as the browser is concerned.

[EDIT]: I didn't mention it upfront, so the posters who answered "Flash" are valid enough, but part of what I'm doing is an attempt to highlight what can be done with pure HTML5... so Flash is right out in my case. (Though it's a perfectly valid answer for anyone doing a "real" web app.) That being the case it looks like I'm out of luck unless I want to involve the server. Thanks anyway!

Answer 1

Simple solution for HTML5 ready browsers...

function download(filename, text) {     var pom = document.createElement('a');     pom.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));     pom.setAttribute('download', filename);      if (document.createEvent) {         var event = document.createEvent('MouseEvents');         event.initEvent('click', true, true);         pom.dispatchEvent(event);     }     else {         pom.click();     } } 

Usage

download('test.txt', 'Hello world!');