Highlight

    function emphasise() {
        var container = document.getElementById('body');
        var what = 'defeasible';
        var spanClass = 'highlight';
        var content = container.innerHTML,
        pattern = new RegExp('(>[^<.]*)('+ what + ')([^<.]*)', 'g'),
        replaceWith = '$1<span '+ (spanClass ? 'class="' + spanClass + '"' : '') + '">$2</span>$3',
        highlighted = content.replace(pattern, replaceWith);
        return (container.innerHTML = highlighted) !== content;
    }