1、Array.isArray()
console.log(Array.isArray([])) //true
2、instanceof
console.log([] instanceof Array) //true
3、constructor
console.log([].constructor == Array) //true
4、Object.proptype.toString()
function isArray(arr){
return Object.prototype.toString.call(arr) == "[object Array]"
}
console.log(isArray([])) //true
