Get value from anonymous function

Question

I have this function that converts a image url to base64 string when i call the function i lost the globalvar data.

Script:

    function convertImgToBase64(url, callback, outputFormat){
    var img = new Image();
    img.crossOrigin = 'Anonymous';
    img.onload = function(){
        var canvas = document.createElement('CANVAS');
        var ctx = canvas.getContext('2d');
        canvas.height = this.height;
        canvas.width = this.width;
        ctx.drawImage(this,0,0);
        var dataURL = canvas.toDataURL(outputFormat || 'image/png');
        callback(dataURL);
        canvas = null;
    };
    img.src = url;
}

And call

        convertImgToBase64(url, function(base64Img){
            //console.log(imageData);
            globalvar = base64Img;
        });

But globalvar lose the data after exit from anonymous function. How can I access the value after the function?

How do you use `globalvar` ? Since the callback is asynchronous, depending on your `load`, you will have to do everything inside your callback as there is no other point where you can be sure of `globalvar`s contents. — somethinghere, Oct 12 '15 at 12:27
@IonVasile again, you are forgetting that your callback gets executed when the image is loaded, but any work that uses `ImageData` _before_ that event will see `imageData` as undefined. Check Juhana's link. — somethinghere, Oct 12 '15 at 12:30
Again, this is because your ajax call gets executed _before_ the image has loaded. Use callbacks appropriately, containing all code that needs this value to be set - and check @Juhana's duplicate link. — somethinghere, Oct 12 '15 at 12:32
Ok but I am in a if else. So is something like this: if ..... globalvar = x; jQuery.ajax({ ....globalvar... }); else convertImgToBase64(url, function(base64Img){ jQuery.ajax({ ....base64Img... }); And I dont want to have the ajax code twice because is little long code. — Sebastian Corneliu Vîrlan, Oct 12 '15 at 12:48
Then simply wrap your ajax in a function and call that from inside your callback? — somethinghere, Oct 12 '15 at 12:49

Get value from anonymous function

0 Answers0