尝试在javascript中加载时绘制图像

Question

i want to call a function on load and it not working its in a iframe if that makes a difference. dont mind the html; thank you in advance.

var canvas = document.getElementById('my_canvas');
var ctx = canvas.getContext('2d');
canvas.width = 320;
canvas.height = 240;
var back = new Image();
var reg = new Image();
var spicy = new Image();
var nosauce = new Image();
var setup1 = setup();
function setup(){
back.src = "selectback.png";
reg.src = "reg.png";
spicy.src = "spicy.png";
nosauce.src = "sauce.png";
back.onload = function(){
ctx.drawImage(back, 0, 0, 321, 241);
};
}
function back(){
var test = new Image();
    test.onload = function() {
        ctx.drawImage(test, 0, 0, 300, 300);
    };
}
window.onload = function () { setup(); }

Answer 1

do this:

document.getElementById('YourIframeId').onload = function() {
setup();
// put your awesome code here
};