Method of judging that the object is an array

Method of judging that the object is an array

1. Array.isArray(a);
2. a.constructor.name　=> "Array"
3. Object.prototype.toString.call(a)==="[object Array]" It can be judged for all basic data types, including null or undefined
4. a instanceof Array
5. a.__proto__===Array.prototype
6. Array.prototype.isPrototypeOf(a)