What is the equivalent function for php explode in Javascript?
There is no explode function in java script.but we can handle the explode functionality by writing some custom functions. here is a simple java script  code for you.
If you Run the following code
explode(’. ‘, ‘blog.altmint.com);
It Could return
1.{0: ‘blog’, 1: ‘altmint’, 2: ‘com’}

function explode( delimiter, string, limit [...]

how to change the Properties of class or id with javascript?
It is very simple with jquery. we can alter or add any css property to the class or id. here is a sample example for it.
Assuming Jquery is Included
$(”#IdName”).css(”color”,”red”);
(or)
$(”.Classname”).css(”color”,”red”);