方法一: typeof
var arr = []
console.log(typeof arr ); 
方法二: instanceof
var arr = []
console.log(arr instanceof Array)方法三: constructor
var arr = []
console.log(arr.constructor == Array)方法一: typeof
var arr = []
console.log(typeof arr ); 
方法二: instanceof
var arr = []
console.log(arr instanceof Array)方法三: constructor
var arr = []
console.log(arr.constructor == Array)