## 判断一个变量是否为数组 1. typeof - typeof 返回类型有7种：string number boolean undefined Function Object Symbol(es6) - typeof 不能判断数组类型 - typeof 返回的值为字符串， ```js alert(typeof a == "string") --> true alert(typeof a == String) --> false ``` ```js function test(){} console.log(typeof 1); // number console.log(typeof test); // function console.log(typeof "yunxi"); // string console.log(typeof undefined); // undefined ``` 2. instanceof ```js console.log([] instanceof Array); // true console.log(/\d+/g instanceof Array); // false ``` 3. constructor ```js console.log(arr.constructor == Array); // true ``` 4. Array.isArray(数组) ```js Array.isArray(state.car) //true ```