JavaScript中清空数组的三种方式

var ary = [1,2,3,4]; 
ary.splice(0,ary.length); 
console.log(ary); // 输出 []，空数组，即被清空了 

int[] ary = {1,2,3,4}; 
ary.length = 0; 

var ary = [1,2,3,4]; 
ary.length = 0; 
console.log(ary); // 输出 []，空数组，即被清空了 

var ary = [1,2,3,4]; 
ary = []; // 赋值为一个空数组以达到清空原数组 

var a = []; 
for (var i=0; i< 1000000; i++){ 
 a.push(i); 
} 
var start = new Date(); 
//a = []; 
a.length = 0; 
var end = new Date(); 
alert(end - start);