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

In addition to all the above, one should note that, for a defined value v:

• String(v) calls v.toString()
• '' + v calls v.valueOf() prior to any other type cast

So we could do something like:

var mixin = {
  valueOf:  function () { return false },
  toString: function () { return 'true' }
};
mixin === false;  // false
mixin == false;    // true
'' + mixin;       // "false"
String(mixin)     // "true"

Tested in FF 34.0 and Node 0.10

Answer 2

On this page you can test the performance of each method yourself :)

http://jsperf.com/cast-to-string/2

here, on all machines and browsers, ' "" + str ' is the fastest one, (String)str is the slowest