js判断是否为数组的3种方法

var ret;
 var o = [1,2,3];
 var toStr = {}.toString;
 var array = {};
 array["[object Array]"] = "array";
 
 console.log("各种判断是否数组的速度比较！")
 
 console.log("方法一：Array.isArray(o)");
 console.time("first");
 for (var i=0;i<10000;i++){
  ret = Array.isArray(o);
 }
 console.timeEnd("first");
 console.log(ret);

 console.log("方法二：o instanceof Array");
 console.time("second");
 for (var i=0;i<10000;i++){
  ret = o instanceof Array;
 }
 console.timeEnd("second");
 console.log(ret);
 
 console.log("方法三：o.constructor == Array");
 console.time("thirth");
 for (var i=0;i<10000;i++){
  ret = o.constructor == Array;
 }
 console.timeEnd("thirth");
 console.log(ret);

 console.log("方法四：array[toStr.call(o)] == 'array'");
 console.time("forth");
 for (var i=0;i<10000;i++){
  ret = array[toStr.call(o)] == "array";
 }
 console.timeEnd("forth");
 console.log(ret);