Determine whether the variable is an array

1. isArray()

        isArray() method is used to determine whether an object is an array. Return if the object is an array  true, otherwise return  false.

Array.isArray(arr); // true

2. Object prototype

        Use the prototype chain to determine whether it has the top of the same prototype chain as the array.

arr.__proto__ === Array.prototype; // true

Three, instanceof operator

        Used to detect whether the properties of the constructor  prototype appear on the prototype chain of an instance object

arr instanceof Array; // true

四、Object.prototype.toString.call()

        All primitive data types can be judged by this method, which is universal

Object.prototype.toString.call(arr); // "[object Array]"
Object.prototype.toString.call(2); // "[object Number]"
Object.prototype.toString.call(""); // "[object String]"
Object.prototype.toString.call(true); // "[object Boolean]"
Object.prototype.toString.call(undefined); // "[object Undefined]"
Object.prototype.toString.call(null); // "[object Null]"
Object.prototype.toString.call(Math); // "[object Math]"
Object.prototype.toString.call({}); // "[object Object]"
Object.prototype.toString.call([]); // "[object Array]"
Object.prototype.toString.call(function () {}); // "[object Function]"

Reprint: Several methods to determine whether a variable is an array - short book