object.is is a polyfill for the es6 egal function: http://wiki.ecmascript.org/doku.php?id=harmony:egal

objectis.js

module.exports = Object.is || 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;
};