how to return value from this javascript function

Question

I'm working with html2canvas and I have the next function

hml2canvas($('body'), {
   onrendered: function(canvas) {           
         data = canvas.toDataURL('image/jpeg');
    }
});

Now, I want to return the data value, so I tried this

html2canvas($('body'), {
    onrendered: (this, imgBase64)         
});

var data;
function imgBase64(canvas) {
     data = canvas.toDataURL('image/jpeg');
}
console.log(data);

but when I see the console I get "undefined". If I put console.log(data); inside the imgBase64 function I get the base64 of the image, but I need the data out of that function to make another work with it. Any ideas? Thanks.

You're logging `data` before the `imgBase64` is ever called. — Jack, Feb 05 '13 at 20:50
See if this helps: http://stackoverflow.com/search?q=asynchronous+variable+javascript — elclanrs, Feb 05 '13 at 20:51
what are you trying to accomplish with `onrendered: (this, imgBase64)`? I'm not even sure that's valid syntax. — jbabey, Feb 05 '13 at 20:52
Asynchronous code explained through Ajax: http://stackoverflow.com/q/14220321/1331430 the same principle applies. — Fabrício Matté, Feb 05 '13 at 20:54
@jbabey: Technically it is valid syntax, two expressions separated by a comma operator but probably not what OP intended to do. Check this jsbin, it throws all sorts of warnings but the code works http://jsbin.com/ucomir/1/edit — elclanrs, Feb 05 '13 at 20:56
The comma operator will return the last expression's return value after evaluating the expressions. — Fabrício Matté, Feb 05 '13 at 20:58
Minifiers use the comma operator everywhere, it's quite useful in one liner return statements, ie `return this.foo = 'foo', this;` — elclanrs, Feb 05 '13 at 21:04
@elclanrs thanks but the link didn't work for me. About this [comment](http://stackoverflow.com/questions/14716630/how-to-return-value-from-this-javascript-function#comment20586257_14716630) what should be the proper way? — Jefferson, Feb 05 '13 at 21:32

score 0 · Accepted Answer · edited May 23 '17 at 10:32

0

I found this answer so I modified to adapt to my needs.

var html2obj = html2canvas($('body'));
var queue  = html2obj.parse();
var canvas = html2obj.render(queue);
var data = canvas.toDataURL('image/jpeg');

this way I have the data to use later.

edited May 23 '17 at 10:32

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answered Feb 05 '13 at 22:17

Jefferson

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how to return value from this javascript function

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