<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<meta name="author" content="杨欣">
<title>filter</title>
</head>
<body>
<script>
Array.prototype.my_filter = function (callback) {
if (!Array.isArray(this) || !this.length || typeof callback !== 'function') {
return []
} else {
let result = [];
for (let index = 0; index < this.length; index++) {
const element = this[index];
if (callback(element, index, this)) {
result.push(element)
}
}
return result
}
}
let arr = [1, 2, 3, 4, 5]
let res = arr.my_filter((ele, i) => {
return ele % 2 === 0
})
console.log(res)//[2,4]
</script>
</body>
</html>原文：https://www.cnblogs.com/samsara-yx/p/12212829.html