if function does not exist write function - javascript

Question

In php I\'m writing the following

In javascript I wish to test if the

Answer 1

You should use strict comparison operator !==

if(typeof myFunction !== 'function'){
    window.myFunction = function(){}; // for a global function or
    NAMESPACE.myFunction = function(){}; // for a function in NAMESPACE 
}

Also try to keep js functions inside namespaces, this way you avoid collisions with other js libraries in the future.