How to check if an object is an array?

Question

I\'m trying to write a function that either accepts a list of strings, or a single string. If it\'s a string, then I want to convert it to an array with just the one item so

Answer 1

I do this in a very simple way. Works for me. Any drawbacks?

Array.prototype.isArray = true;

a=[]; b={};
a.isArray  // true
b.isArray  // (undefined -> false)