Different browsers have separate implementation of JavaScript
<p>I am new to JavaScript. I am referring to a page on JavaScript framework: <a href="http://www.ibm.com/developerworks/web/library/wa-jsframeworks/" rel="nofollow">What is a JavaScript framework?</a></p>

<p>I know JavaScript is for the web client side. It is a object-oriented script language. The link above writes:</p>

<blockquote>
  <p>Using JavaScript, however, is not an easy task, primarily due to the complications that arise when trying to provide support for multiple Web browsers.</p>
  
  <p>Like HTML and CSS, different browsers have separate implementations of JavaScript, and it can be a nightmare to ensure that your JavaScript code is cross-browser compatible.</p>
</blockquote>

<p>The second part says different browsers has different implementations. Why?
Since JavaScript is just a language like Java, C etc. Why do different browsers need different implementations?</p>

<p>As long as the JavaScript language specification is released, each browser should follow the language requirement. So why they have different implementations?
What does the implementation here mean?</p>

<hr>

<p>EDIT:</p>

<p>JavaScript is <strong>NOT</strong> a object-oriented language! It is a language based on objects!</p>
