## 参数默认值 ``` function show(a, b = 'hello') { console.log(a, b); } ``` ## 参数解构函数 ``` function foo({name = 'jack', age = 20} = {}) { //注意,这里是等号 console.log(name, age); } //如果是调用的解构对象,一定要传参,否则会报错,或者像上面一样, 等于一个空对象 foo({ name: 'milan', age: 50, }) ``` ## rest参数(剩余参数) ``` function foo(a,...rest) { console.log(a,rest) } foo(1,2,3,4) ``` 结果 ``` 1 (3) [2, 3, 4] //把剩余的参数都放进了后面的数组中 ``` ## ...扩展运算符 ``` console.log(...[1,2,3]); ``` 结果,把一个数组拆散 ``` 1 2 3 ``` ``` function counter(a, b, c) { console.log(a + b + c); } counter(...[1, 2, 3]); ``` ### 合并数组 ``` var arr1 = [1, 2, 3]; var arr2 = [4, 5, 6]; var arr3 = [...arr1, ...arr2]; console.log(arr3); ```