Create SVG tag with JavaScript
.createElementNS is the required method for both the svg and path elements. Example below.
var svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
var path1 = document.createElementNS("http://www.w3.org/2000/svg", 'path');
var path2 = document.createElementNS("http://www.w3.org/2000/svg", 'path');
svg.setAttribute("aria-hidden","true");
svg.setAttribute('viewbox', '0 0 24 24');
svg.setAttribute('width', '24px');
svg.setAttribute('height', '24px');
path1.setAttribute('d', 'M0 0h24v24H0z');
path1.setAttribute('fill', 'none');
path2.setAttribute('d', 'M12 2C6.48 2 2 6.48 2 12s4.48 10 10 10 10-4.48 10-10S17.52 2 12 2zm-1 17.93c-3.95-.49-7-3.85-7-7.93 0-.62.08-1.21.21-1.79L9 15v1c0 1.1.9 2 2 2v1.93zm6.9-2.54c-.26-.81-1-1.39-1.9-1.39h-1v-3c0-.55-.45-1-1-1H8v-2h2c.55 0 1-.45 1-1V7h2c1.1 0 2-.9 2-2v-.41c2.93 1.19 5 4.06 5 7.41 0 2.08-.8 3.97-2.1 5.39z');
path2.setAttribute('fill', '#2962ff');
svg.appendChild(path1);
svg.appendChild(path2);
document.body.appendChild(svg);You forgot the Namespace URI of your svg element and xmlns attribute.
Also, version is ignored by all browsers.
var svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
svg.setAttribute('style', 'border: 1px solid black');
svg.setAttribute('width', '600');
svg.setAttribute('height', '250');
svg.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns:xlink", "http://www.w3.org/1999/xlink");
document.body.appendChild(svg);