Why do we need different JS for different browsers
<p>What exactly are different things we need to take care when writing different JS files, like arrays, variables etc., Is there a book or website explaining differences between different JS engines used for browsers?</p>

<p>I was working on something in our application and bumped into a JS issue and was looking for solution and found out that we might need 2 different JS for different browsers to get my exact functionality. Why is that? Is that the browsers use different JS engines so they understand my JS in different ways?</p>
