ignoring fuzzy match and add exact word pattern matching using javascript

Question

I am trying to create a text highlight option for my website. But I want exact word match instead of fuzzy word match, The code that I have matches all kind of instances and it has some case sensitivity issues. If we take the Jfiddle example, I only want to add the word cancer, case sensitivity should nt be an issue. and ignore fuzzy matches, like cancerous and bycanceraous(I know there is not a word like that, but could not think of any for the example). I have the jfiddle link http://jsfiddle.net/ehzPQ/6/

HTML:

<div id="entity">cancer</div>
<div id="article">
  This kind of insurance is meant to supplement health insurance for cancerous-care costs. But generally you're better off putting your money toward comprehensive health policies. The I just repeat health insurance, because it sounds so good! health insurance, health insurance, I can never grow tired of it... Cancer is seriously a dangerouse disease. Test case : bycanceraous
</div>​

CSS:

.highlight {
    background-color: yellow
}​

Javascript:

$(document).ready(function(){
  var $test = $('#article');
  var entityText = $('#entity').html();
  var entityRegularExpression = new RegExp(entityText,"g");
  var highlight = '<span class="highlight">' + entityText + '</span>';
  $test.html($test.html().replace(entityRegularExpression, highlight));
});

Answer 1

You need to utilize Regular Expression's Word Boundaries.

Change the following line:

var entityRegularExpression = new RegExp(entityText, "g");

To this:

var entityRegularExpression = new RegExp("\\b" + entityText + "\\b", "gi");

Here's the updated jsfiddle.
Note: I updated the article text to contain some instances of the word so you could see it work.

You can also take it a step further and have the case insensitive matches retain their original case, by utilizing Regular Expression's Callbacks. Check out this jsfiddle for the code and example.