Creating an xls or csv file from a Javascript variable

I have an app that uses Javascript to perform some calculations and then plot the data, but I'd like to add the option for the user 开发者_如何转开发to be able to actually download the data into a csv or xls file.

Is there a way in Javascript (or some other method) to have the user press a button, then it will prompt them for the name of the file to save it as, and it will then create a comma-delimited or excel spreadsheet?

Thanks!

EDIT:

Thanks for all the suggestions everyone. Wish I could mark you all as answers, but upboats will have to do for now

It's not hard to open a window and write the csv into it. But I don't know of any way for javascript to change the Content-Type: header. And without that it won't prompt to save or open.

You'll need assistance from the server to do this. You can send the data to the server in a form variable and have the server send it right back with the correct header Content-type: text/csv you may also want the Content-Disposition: header to give your file a name.

Yes, but you'll need to use server-side code as well. Use JavaScript to construct a link to a page that streams the csv data back as an attachment. The server output should contain a content-disposition header of attachment; filename="fileName.csv".

No, you can't create and/or save a file directly from JavaScript. On some browsers/platforms (IE/Windows), you could create and write to a file via ActiveX object:

function WriteToFile()
{
var fso = new ActiveXObject("Scripting.FileSystemObject");
var s = fso.CreateTextFile("C:\\temp\\Test.txt", true);
s.WriteLine('Hello');
s.Close();
}

Another solution is to use client-side JavaScript (inside a browser) to output CSV data into a separate window (or pop-up) and have a user to copy/paste it into Excel.

If you want to do it in a browser website style it might be hard. But Javascript is a good language to do this, but you will need to use .hta instead of a normal .html. Creating an .hta creates a stand alone application just like a normal .exe.

Here is what you want to look for ActiveXObject("Excel.Application")

In order to transform a html into an hta, here is the tag

<HTA:APPLICATION
  id="SomeId"
  border="thin"
  borderStyle="normal"
  caption="yes"
  maximizeButton="yes"
  minimizeButton="yes"
  showInTaskbar="yes"
  windowState="yes"
  innerBorder="yes"
  navigable="yes"
  scroll="auto"
  scrollFlat="yes"
  singleinstance="yes"
/>

For futher reading on hta and the excel active X

You could certainly write a browser plugin (ActiveX control on IE, NPAPI on others) with FireBreath that would do this; you'd have to write it in C++. Honestly, I agree with others in suggesting that you do this server-side instead, but you can do it with a plugin and it wouldn't be too difficult.

I think that it would be possible to do this (up to a certain size limit) with data URIs