html5 - javascript / canvas5 error from simple code -

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error: uncaught exception: [exception... "component returned failure code: 0x80040111 (ns_error_not_available) [nsidomcanvasrenderingcontext2d.drawimage]" nsresult: "0x80040111 (ns_error_not_available)" location: "js frame :: http://127.0.11.1/test/canvas5_b.php :: setup :: line 27" data: no]

function setup() {      var e = document.getelementbyid("mycanvas");     var ctx = e.getcontext('2d');       var meter = new image();     meter.src = "meter.jpg";     var meter_bar = new image();     meter_bar.src = "meter_bar.jpg";     //alert(meter);      ctx.beginpath();/////////line 27////////////     ctx.drawimage(meter, 50, 100);     //ctx.globalcompositeoperation = "lighter";     ctx.drawimage(meter_bar, 68, 123);     ctx.closepath();   }  window.onload = setup;

both images in right folder. thing gets me works if put alert(meter); before line 27. if not loaded, have running on window.onload, dont see how is.

edit : issue of when image loaded (ty rob). appears best globally declare , set image src, , call window.onload = setup, : (correct me if bad)

var img1, img2; img1 = new image(); img2 = new image(); //declare , set images src img1.src = "meter.jpg"; img2.src = "meter_bar.jpg";  var canvasheight, canvaswidth; canvasheight = 300; canvaswidth= 600;  var ctx;   function setup() {     var e = document.getelementbyid("mycanvas");     ctx = e.getcontext('2d');     draw(); }  function draw() {     ctx.clearrect(0,0,canvaswidth, canvasheight);     ctx.beginpath();     ctx.drawimage(img1, 50, 100);     ctx.drawimage(img2, 68, 123);     ctx.closepath(); }  window.onload = setup;

make sure images loaded first. instance:

 var img = new image();  img.onload = function(){     ctx.drawimage(img,0,0);     }   // put after onload, otherwise onload may   // not called if image in cache  img.src = 'whatev.png';

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