function inherits(child, parent) { var _proptotype = Object.create(parent.prototype); _proptotype.constructor = child.prototype.constructor; child.prototype = _proptotype; } function People(name, age) { this.name = name; this.age = age; } People.prototype.getName = function () { return this.name; } function English(name, age, language) { People.call(this, name, age); this.language = language; } inherits(English, People); English.prototype.introduce = function () { console.log('Hi, I am ' + this.getName()); console.log('I speak ' + this.language); } function Chinese(name, age, language) { People.call(this, name, age); this.language = language; } inherits(Chinese, People); Chinese.prototype.introduce = function () { console.log('你好，我是' + this.getName()); console.log('我说' + this.language); } var en = new English('Byron', 26, 'English'); var cn = new Chinese('色拉油', 27, '汉语'); en.introduce(); cn.introduce();
ES6 class 与继承
"use strict"; class People{ constructor(name, age){ this.name = name; this.age = age; } getName(){ return this.name; } } class English extends People{ constructor(name, age, language){ super(name, age); this.language = language; } introduce(){ console.log('Hi, I am ' + this.getName()); console.log('I speak ' + this.language); } } let en = new English('Byron', 26, 'English'); en.introduce();
语法
label statement
loop:
for (var i = 0; i < 10; i++) { for (var j = 0; j < 5; j++) { console.log(j); if (j === 1) { break loop; } } } console.log(i);
语句与表达式
var x = { a:1 }; { a:1 } { a:1, b:2 }
立即执行函数
( function() {}() ); ( function() {} )(); [ function() {}() ]; ~ function() {}(); ! function() {}(); + function() {}(); - function() {}(); delete function() {}(); typeof function() {}(); void function() {}(); new function() {}(); new function() {}; var f = function() {}(); 1, function() {}(); 1 ^ function() {}(); 1 > function() {}();
高阶函数
高阶函数是把函数当做参数或者返回值是函数的函数
回调函数
[1, 2, 3, 4].forEach(function(item){ console.log(item); });
闭包
闭包由两部分组成
1.函数
2.环境：函数创建时作用域内的局部变量
function makeCounter(init) { var init = init || 0; return function(){ return ++init; } } var counter = makeCounter(10); console.log(counter()); console.log(counter());
典型错误
for (var i = 0; i < doms.length; i++) { doms.eq(i).on('click', function (ev) { console.log(i); }); } for (var i = 0; i < doms.length; i++) { (function (i) { doms.eq(i).on('click', function (ev) { console.log(i); }); })(i); }
惰性函数
function eventBinderGenerator() { if (window.addEventListener) { return function (element, type, handler) { element.addEventListener(type, hanlder, false); } } else { return function (element, type, handler) { element.attachEvent('on' + type, handler.bind(element, window.event)); } } } var addEvent = eventBinderGenerator();
柯里化
一种允许使用部分参数生成函数的方式
function isType(type) { return function(obj){ return Object.prototype.toString.call(obj) === '[object '+ type +']'; } } var isNumber = isType('Number'); console.log(isNumber(1)); console.log(isNumber('s')); var isArray = isType('Array'); console.log(isArray(1)); console.log(isArray([1, 2, 3])); function f(n) { return n * n; } function g(n) { return n * 2; } console.log(f(g(5))); function pipe(f, g) { return function () { return f.call(null, g.apply(null, arguments)); } } var fn = pipe(f, g); console.log(fn(5));
尾递归
1.尾调用是指某个函数的最后一步是调用另一个函数
2.函数调用自身，称为递归
3.如果尾调用自身，就称为尾递归
递归很容易发生"栈溢出"错误（stack overflow）
function factorial(n) { if (n === 1) return 1; return n * factorial(n - 1); } factorial(5) // 120
但对于尾递归来说，由于只存在一个调用记录，所以永远不会发生"栈溢出"错误
function factorial(n, total) { if (n === 1) return total; return factorial(n - 1, n * total); } factorial(5, 1) // 120
柯里化减少参数