判断一个变量是否为数组的几种方法

var arr =[1,2,3];
console.log(arr instanceof Array);  //true;

var  arr =[1,2,3];
console.log(arr.constructor===Array);  //true;

var arr = [1,2,3,1];
var arr2 = [{ abac : 1, abc : 2 }];
function isArrayFn(value){
if (typeof Array.isArray === "function") {
return Array.isArray(value);
}else{
return Object.prototype.toString.call(value) === "[object Array]";
}
}
alert(isArrayFn(arr));// true
alert(isArrayFn(arr2));// true