You should get 2 alerts of this page
var svg = new Image();
svg.onload = function() { alert('svg loaded'); };
svg.src = "/svg/symbolCheck.svg";

var png = new Image();
png.onload = function() { alert('png loaded'); };
png.src = "/png/0x2620.160.png";

// Only if image is added to dom, Opera fires onload
// document.body.appendChild(svg);