十五. 对象的扩展

1. Object.is 判断两个值是否完全相等

console.log(Object.is(120,120));      // ===
console.log(Object.is(NaN,NaN));      // ===
console.log(NaN === NaN);            // ===

2. Object.assign 对象的合并

3. Object.setPrototypeOf 设置原型对象 Object.getPrototypeOf