gistfile1.js

    // replacer is a function that receives the full matched string
    // as the first argument and the regex's groups as the following
    // arguments (similar to https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace#Specifying_a_function_as_a_parameter,
    // except "offset" and "string"). It can return either a simple string,
    // or a full DOM node.
    //
    // node is the document node from which to start (i.e. descend from)

    function replaceTextWithElement(node, regex, replacer, skipCode) {
        var len,
            i;
            
        if (node.nodeType !== 3) {
            if (skipCode && node.nodeName.toLowerCase() === "code")
                return;
            
            var childNodes = node.childNodes,
                children = [];
            len = childNodes.length;
            
            // We're altering the dom, and childNodes is a live collection. Hence we have to make
            // a copy at this point.
            for (i = 0; i < len; i++)
                children.push(childNodes[i]);
            
            for (i = 0; i < len; i++) {
                replaceTextWithElement(children[i], regex, replacer, skipCode);
            }
            return;
        }
        
        regex.lastIndex = 0;
        var text = node.nodeValue,
            match,
            result = [],
            start = 0,
            first = true;

        while (match = regex.exec(text)) {
            first = start === 0;
            if (match.index > start) {
                result.push(text.substring(start, match.index))
                first = true;
            }
            start = regex.lastIndex;
            result.push(replacer.apply({isFirst: first}, match));
        }

        if (!result.length)
            return;
        
        if (start < text.length)
            result.push(text.substring(start));

        var parent = node.parentNode, val;
        len = result.length;
        
        for (i = 0; i < len; i++) {
            val = result[i];
            if (typeof val === "string") {
                val = document.createTextNode(val);
            }
            parent.insertBefore(val, node);
        }
        parent.removeChild(node);
    }