把对象的值复制到另一个对象

let books = {};
Object.assign(
	books,//源对象
	{"js":"javascript"}//要插入的对象
);
console.log(books);//{js: "javascript"}
Object.assign(
	books,
	{"h5":"html5"}
);
console.log(books);//{js: "javascript", h5: "html5"}