筛选原来数组中满足要求的元素，再将它赋值给新数组
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
var arr=[3,45,63,23,56,22,11,65,25,67,84,26];
var newarr=[];
for (var i=0;i<arr.length;i++)
{
if(arr[i]>50)
newarr[newarr.length]=arr[i];
}
alert(newarr);
</script>
</body>
</html>看看第二个方法有什么不足之处
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
var arr=[3,45,63,23,56,22,11,65,25,67,84,26];
var newarr=[];
var j=0;
for (var i=0;i<arr.length;i++)
{
if(arr[i]>50)
newarr[j]=arr[i];
j++;
}
alert(newarr);
</script>
</body>
</html>