deep-equals.js

function deepEquals(x, y) {
  if (x === y)               return true;
  if (x !== x)               return y !== y;
  if (typeof x !== typeof y) return false;
  if (typeof x !== 'object') return false;

  var typeX = getType(x);
  var typeY = getType(y);

  if (typeX !== typeY)       return false;
  if (typeX === 'date'  )    return +x === +y;
  if (typeX === 'array' )    return deepEqualsArray(x, y);
  if (typeX === 'regexp')    return ((x + "") === (y + ""));
  if (typeX === 'object')    return deepEqualsObject(a, b);

  return false;
}

function deepEqualsArray(x, y) {
  return x.length === y.length &&
    x.every((xx, i) => deepEquals(xx, y[i]));
}

function getType(x) {
  var type = Object.prototype.toString.call(x);
  return type.substring(8, type.length - 1 ).toLowerCase();
}

function deepEqualsObjects(x, y) {
  var keysX = Object.keys(x);
  var keysY = Object.keys(y);
  return deepEqualsArray(keysX.sort(), keysY.sort()) &&
    keysX.every(k => deepEquals(x[k], y[k]));
}                       

console.log(deepEquals(NaN, NaN));
console.log(deepEquals(1, 1));
console.log(deepEquals(1, 2));
console.log(deepEquals([1,2], [1,2]));
console.log(deepEquals([1,2], [1,3]));
console.log(deepEquals(/abc+\/\/\/\gA*/, new RegExp(/abc+\/\/\/\gA*/)));