Tweaks to rnocache

JavaScript performance comparison

Test case created by Charles McNulty and last updated


Jquery uses the rnocache regex for determining problematic html tags for both caching and for the use of innerHtml. The problem is that these two purposes share very little overlap, and conflating them results in not using innerHtml in places where it's perfectly safe, and much faster.

For discussion and bug see:

To implement the test, I extend jquery with a .html2() function which is a direct copy of the 1.5.1 version of .html(), but add a new regex test:

rnoInnerhtml = /<script|<style/i

which I use in place of rnocache within the .html. This change allows me to then copy a select box using innerHTML rather than .empty().append() which results in some rather large speed increases.

Preparation code

<script src=""></script>
<div>Original: <div id="source"><select id="test_select" name="test_select">
        <option label="1">0</option>
        <option label="1">1</option>
        <option label="2">2</option>
        <option label="3" selected="selected">3</option>
        <option label="4">4</option>
        <option label="1">5</option>
        <option label="2">6</option>
        <option label="3">7</option>
        <option label="4">8</option>
        <option label="1">9</option>
Following two selects should be identical:
<div>Unoptimized copy: <div id="destination"></div></div>
<div>Optimized copy:<div id="destination2"></div></div>
  var rinlinejQuery = / jQuery\d+="(?:\d+|null)"/g,
      rleadingWhitespace = /^\s+/,
      rxhtmlTag = /<(?!area|br|col|embed|hr|img|input|link|meta|param)(([\w:]+)[^>]*)\/>/ig,
      rtagName = /<([\w:]+)/,
      rtbody = /<tbody/i,
      rhtml = /<|&#?\w+;/,
      rnoInnerhtml = /<script|<style/i,
      rnocache = /<(?:script|object|embed|option|style)/i,
      // checked="checked" or checked (html5)
      rchecked = /checked\s*(?:[^=]|=\s*.checked.)/i,
      wrapMap = {
    option: [1, "<select multiple='multiple'>", "</select>"],
    legend: [1, "<fieldset>", "</fieldset>"],
    thead: [1, "<table>", "</table>"],
    tr: [2, "<table><tbody>", "</tbody></table>"],
    td: [3, "<table><tbody><tr>", "</tr></tbody></table>"],
    col: [2, "<table><tbody></tbody><colgroup>", "</colgroup></table>"],
    area: [1, "<map>", "</map>"],
    _default: [0, "", ""]
  wrapMap.optgroup = wrapMap.option;
  wrapMap.tbody = wrapMap.tfoot = wrapMap.colgroup = wrapMap.caption = wrapMap.thead; =;
  // IE can't serialize <link> and <script> tags normally
  if (! {
   wrapMap._default = [1, "div<div>", "</div>"];
   html2: function(value) {
    if (value === undefined) {
     return this[0] && this[0].nodeType === 1 ? this[0].innerHTML.replace(rinlinejQuery, "") : null;
     // See if we can take a shortcut and just use innerHTML
    } else if (typeof value === "string" && !rnoInnerhtml.test(value) && ( || !rleadingWhitespace.test(value)) && !wrapMap[(rtagName.exec(value) || ["", ""])[1].toLowerCase()]) {
     value = value.replace(rxhtmlTag, "<$1></$2>");
     try {
      for (var i = 0, l = this.length; i < l; i++) {
       // Remove element nodes and prevent memory leaks
       if (this[i].nodeType === 1) {
        this[i].innerHTML = value;
      // If using innerHTML throws an exception, use the fallback method
     } catch (e) {
    } else if (jQuery.isFunction(value)) {
     this.each(function(i) {
      var self = jQuery(this);
      self.html(, i, self.html()));
    } else {
    return this;
  var template = $("#source").html();

Preparation code output

Following two selects should be identical:
Unoptimized copy:
Optimized copy:

Test runner

Warning! For accurate results, please disable Firebug before running the tests. (Why?)

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Testing in unknown unknown
Test Ops/sec
using standard nocache
using innerHTML optimized regex

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