Object.is polyfill

gistfile1.js

// Blatantly stolen from ES6 specs. Kept here for reference.
// http://wiki.ecmascript.org/doku.php?id=harmony:egal

if(!Object.is) {

  Object.defineProperty(Object, 'is', {
    value: function(x, y) {
      if (x === y) {
        // 0 === -0, but they are not identical
        return x !== 0 || 1 / x === 1 / y;
      }
       
      // NaN !== NaN, but they are identical.
      // NaNs are the only non-reflexive value, i.e., if x !== x,
      // then x is a NaN.
      // isNaN is broken: it converts its argument to number, so
      // isNaN("foo") => true
      return x !== x && y !== y;
    },
    configurable: true,
    enumerable: false,
    writable: true
  });

}