How to determine if Native JavaScript Object has a Property/Method?

Question

I thought this would be as easy as:

if(typeof(Array.push) == \'undefined\'){
  //not defined, prototype a version of the push method
  // Firefox never gets          


        

Answer 1

And it does work fine in Firefox

That's only by coincidence! You can't generally expect a prototype's method to also exist on the constructor function.

if(typeof(Array().push) == 'undefined')

This was nearly right except you forget new, a perennial JavaScript gotcha. new Array().push, or [].push for short, would correctly check an instance had the method you wanted.