how can i convert object value into string value using javascript?

You can just use the string object like that.What are you trying to convert.

<cpde>
var stringObj = new String ("string");


you could just use this stringObj it would give you the value only.

More on JS Strings visit =>
http://www.w3schools.com/jsref/jsref_obj_string.asp[^]

If you have number object you can use toString() method
something like -

var n= new Number(1);
n.toString();

Hope this helps.