[Nexus]

espltd,

<img src="/files/one.jpg">
<div id="blockNews">
<img src="/files/two.jpg">
<img src="/files/three.jpg">
<img src="http://url/files/test.jpg">
</div>
<script type='text/javascript'>
//© ksa
[].forEach.call(document.querySelectorAll('#blockNews img'), function(el){
	var val=el.getAttribute('src');
	if (/^\//.test(val)) {
		el.src = 'http://mysite'+val;
		alert(el.src);
	}
});
</script>