Casting to string in JavaScript

Question

I found three ways to cast a variable to String in JavaScript.
I searched for those three options in the jQuery source code, and they are all in use

Answer 1

They do behave differently when the value is null.

• null.toString() throws an error - Cannot call method 'toString' of null
• String(null) returns - "null"
• null + "" also returns - "null"

Very similar behaviour happens if value is undefined (see jbabey's answer).

Other than that, there is a negligible performance difference, which, unless you're using them in huge loops, isn't worth worrying about.