CODEWITHSUNDEEP
javascriptvariables
Nejmeddine Jammeli
Nejmeddine Jammeli

Reputation: 1037

Why are these variables "undefined"?

I have the folowing code :

var canvasData;
var canvas2imgval;

imageObj1.onload = function() {
    ctx.drawImage(imageObj1, 0, 0, wdOb1, hgOb1);
    imageObj2.onload = function() {
        ctx.drawImage(imageObj2, imgposLeft, imgposTop, wdOb2, hgOb2);
        //img = c.toDataURL("image/png");
        //document.write('<img src="' + img + '" width="256" height="256"/>');
        //canvas2img
        canvasData = c.toDataURL("image/png");
    }

}
console.log("canvasData : "+canvasData ); 
$("#canvas2img").val(canvasData) ;
canvas2imgval = $("#canvas2img").val() ;
console.log("canvas2imgval1 : "+canvas2imgval );

The problem is when I view the value of both variables, canvasData is undefined and canvas2imgval1 has no value. I don't know what's wrong with my code. Normally those two variables are marked public with the JavaScript keyword var.

Upvotes: 1

Views: 171

Answers (1)

pawel
pawel

Reputation: 36995

You assign values to these variables in image onload event handlers, but try to access them before these handlers are executed.

In order to use these variables you could create a function that will be called after imageObj2.onload executes. I'd also suggest to pass the canvasData as an argument instead of using a global variable (as long as it's not used elsewhere).

var canvas2imgval;
var afterLoad = function(canvasData){
    console.log("canvasData : "+canvasData ); 
    $("#canvas2img").val(canvasData) ;
    canvas2imgval = $("#canvas2img").val() ;
    console.log("canvas2imgval1 : "+canvas2imgval); 
}    

imageObj1.onload = function() {
ctx.drawImage(imageObj1, 0, 0, wdOb1, hgOb1);
    imageObj2.onload = function() {
        ctx.drawImage(imageObj2, imgposLeft, imgposTop, wdOb2, hgOb2);
        //img = c.toDataURL("image/png");
        ////////document.write('<img src="' + img + '" width="256" height="256"/>');
        //canvas2img
        canvasData = c.toDataURL("image/png");
        afterLoad(canvasData);
    }

}

Upvotes: 1

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