In JavaScript, how can I replace text in an HTML page without affecting the tags?

I'm trying to figure out how to do a replace with Javascript. I'm looking at the entire body of the page and would like to replace the keyword matches NOT within an HTML tag.

Here is an example:

<body>
  <span id="keyword">blah</span>
  <div>
    blah blah keyword blah<br />
    whatever keyword whatever
  </div>
</body>

<script type="text/javascript">
var replace_terms = {
  'keyword':{'url':'http://en.wikipedia.org/','target':'_blank'}
}

jQuery.each(replace_terms, function(i, val) {
  var re = new RegExp(i, "gi");
  $('body').html(
    $('body').html().replace(re, '<a href="'+ val['url'] +'" target="'+val['target']+'">' + i + '</a>')
  );
});

</script>

I'm looking to replace all instances of the "keyword" that isn't within an HTML tag (between < and >).

I guess I also need to ignore if "keyword" is within a script or style element.

Answers:

Answer

Don't use regex to parse HTML. [X][HT]ML is not a regular language and cannot reliably be processed using regex. Your browser has a good HTML parser built-in; let that take the strain of working out where the tags are.

Also you don't really want to work on html()/innerHTML on body. This will serialise and re-parse the entire page, which will be slow and will lose any information that cannot be serialised in HTML, such as event handlers, form values and other JavaScript references.

Here's a method using DOM that seems to work for me:

function replaceInElement(element, find, replace) {
    // iterate over child nodes in reverse, as replacement may increase
    // length of child node list.
    for (var i= element.childNodes.length; i-->0;) {
        var child= element.childNodes[i];
        if (child.nodeType==1) { // ELEMENT_NODE
            var tag= child.nodeName.toLowerCase();
            if (tag!='style' && tag!='script') // special case, don't touch CDATA elements
                replaceInElement(child, find, replace);
        } else if (child.nodeType==3) { // TEXT_NODE
            replaceInText(child, find, replace);
        }
    }
}
function replaceInText(text, find, replace) {
    var match;
    var matches= [];
    while (match= find.exec(text.data))
        matches.push(match);
    for (var i= matches.length; i-->0;) {
        match= matches[i];
        text.splitText(match.index);
        text.nextSibling.splitText(match[0].length);
        text.parentNode.replaceChild(replace(match), text.nextSibling);
    }
}

// keywords to match. This *must* be a 'g'lobal regexp or it'll fail bad
var find= /\b(keyword|whatever)\b/gi;

// replace matched strings with wiki links
replaceInElement(document.body, find, function(match) {
    var link= document.createElement('a');
    link.href= 'http://en.wikipedia.org/wiki/'+match[0];
    link.appendChild(document.createTextNode(match[0]));
    return link;
});

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