Inserting arbitrary HTML into a DocumentFragment

Here is a way in modern browsers without looping:

var temp = document.createElement('template');
temp.innerHTML = '<div>x</div><span>y</span>';

var frag = temp.content;

or, as a re-usable

function fragmentFromString(strHTML) {
    var temp = document.createElement('template');
    temp.innerHTML = strHTML;
    return temp.content;
}

UPDATE:
I found a simpler way to use Pete’s main idea, which adds IE11 to the mix:

function fragmentFromString(strHTML) {
    return document.createRange().createContextualFragment(strHTML);
}

The coverage is better than the <template> method and tested ok in IE11, Ch, FF.