<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script>
var arr = [1,2,3,4,5];
Array.prototype.sum = function (){
return eval(this.join(‘+‘));
}
console.time(‘a‘);
console.log(arr.sum());
console.timeEnd(‘a‘);
Array.prototype.sum2 = function (){
var len = this.length;
var num = 0;
for( var i=0;i <len; i++ ){
num += this[i];
}
return num;
}
console.time(‘b‘);
console.log(arr.sum2());
console.timeEnd(‘b‘);
</script>
</head>
<body>
</body>
</html>
eval的性能比for的差很多，因为eval会把字符串转换成javascript语句，然后在执行。转换的过程中是消耗性能最大的地方。
时间： 2024-10-07 19:45:25