svgjs

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/svg.js/2.3.6/svg.min.js"></script>
<div id="canvas"></div>

JavaScript

var draw = SVG('canvas').size(500,500);
var rect = draw.rect(100, 100).attr({ fill: '#f0f' });
console.log(draw.children());
rect.id('test');

console.log(draw.select('#test2').first());
console.log(draw.select('#test2').first().attr({ fill: '#ff0000' }));