1、简述
高阶函数似乎是一种先进编程的的技术。然而，并不是。
高阶函数其实就是将函数作为参数或者返回值的函数。其中作为参数的函数一般是回调函数。
2、例子
（1）最简单的例子
大家都熟悉数组的sort方法。
<!DOCTYPE html><html lang="zh"> ???<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" /> ???????<title>高阶函数</title> ???</head> ???<body> ???????<script type="text/javascript"> ???????????let arr = [1,2,4,3]; ???????????arr.sort((a,b)=>{return a-b}) ???????????console.log(arr) ???????</script> ???</body></html>sort方法的参数就是一个函数（回调函数），这个回调函数决定了如何比较数组中的任意两个元素。
（2）字符换大写
实现一：
<!DOCTYPE html><html lang="zh"> ???<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" /> ???????<title>高阶函数</title> ???</head> ???<body> ???????<script type="text/javascript"> ???????????let arr = [‘abc‘, ‘def‘], ???????????????arrNew = []; ???????????for(let i = 0; i < arr.length; i++) { ???????????????arrNew[i] = arr[i].toUpperCase() ???????????} ???????????console.log(arrNew) ???????</script> ???</body></html>实现二：
<!DOCTYPE html><html lang="zh"> ???<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" /> ???????<title>高阶函数</title> ???</head> ???<body> ???????<script type="text/javascript"> ???????????let arr = [‘abc‘, ‘def‘], ???????????????arrNew = []; ???????????arrNew = arr.map(val => { ???????????????return val.toUpperCase() ???????????}) ???????????console.log(arrNew) ???????</script> ???</body></html>（3）高阶函数实现
若代码中出现重复或者类似的代码，就可以使用高阶函数。如产生一个包含数字的字符串：
<!DOCTYPE html><html lang="zh"> ???<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" /> ???????<title>高阶函数</title> ???</head> ???<body> ???????<script type="text/javascript"> ???????????let digits = ‘‘ ???????????for (let i=0;i<10;i++) { ???????????????digits += i ???????????} ???????????console.log(digits) ???????</script> ???</body></html>使用高阶函数实现：
<!DOCTYPE html><html lang="zh"> ???<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" /> ???????<title>高阶函数</title> ???</head> ???<body> ???????<script type="text/javascript"> ???????????let digits = ‘‘ ???????????function buildString(n, callback) { ???????????????let val = ‘‘; ???????????????for(let i = 0; i < n; i++) { ???????????????????val += callback(i) ???????????????} ???????????????return val ???????????} ???????????digits = buildString(10, i => { ???????????????return i ???????????}) ???????????console.log(digits) ???????</script> ???</body></html>高阶函数简述 js
原文地址：https://www.cnblogs.com/mengfangui/p/9812654.html