replace(regexp/substr, replacetext) Searches and replaces the regular expression (or sub string) portion (match) with the replaced text instead.

gistfile1.txt

//replace(substr, replacetext)
var myString = '999 JavaScript Coders';
console.log(myString.replace(/JavaScript/i, "jQuery"));
//output: 999 jQuery Coders

 

//replace(regexp, replacetext)
var myString = '999 JavaScript Coders';
console.log(myString.replace(new RegExp( "999", "gi" ), "The"));
//output: The JavaScript Coders