Object.assign()

Object.assign()用于将所有可枚举属性的值从一个或多个源对象复制到目标对象

const target = { a: 1, b: 2 };
const source = { b: 4, c: 5 };

const returnedTarget = Object.assign(target, source)

console.log(target);  //{ a: 1, b: 4, c: 5 }
console.log(source); //{ b: 4, c: 5 }
console.log(returnedTarget);  //{ a: 1, b: 4, c: 5 }

const target = { a: 1, b: 2 };

const returnedTarget = Object.assign({}, source)
returnedTarget.a1 = 'a1'

console.log(target);  //{ a: 1, b: 2 }
console.log(returnedTarget);  //{ a: 1, b: 2, a1: "a1" }