Inside the Haunted Hickory House file, developers for the Forest of Function Expressions Theme Park have created a declared function called forestFright. They’ve decided not to keep the function in memory, however, but instead only use it if fierce a…
JavaScript是一种解释型语言,函数声明会在JavaScript代码加载后.执行前被解释,而函数表达式只有在执行到这一行代码时才会被解释. 在JS中有两种定义函数的方式, 1是:var aaa=function(){...} 2是:function aaa(){...} var 方式定义的函数,不能先调用函数,后声明,只能先声明函数,然后调用. function方式定义函数可以先调用,后声明. var func=function 和 function func()在意义上没有任何不同,但其…
One of the key characteristics of function declarations is function declaration hoisting, whereby function declarations are read before the code excutes. That means a function declaration may appear after code that calls it and still work: sayHi(); f…
JS 中 函数.继承.闭包.作用域链... 一直都是硬伤,一碰到这样的问题头就大了.但是如果我继续着说:我不会,就真的无药可救了.要勇敢地说出:我的字典里就没有不会这个词,吼吼..正好昨天在书城里看了本JS红宝书,还没有看完,先记录下: Function-函数在JS中有两种使用方法: (1)函数声明: 声明和调用是没有严格的先后顺序的 Greet(); //executed correctly. there is not the strict order between declaration…
全局命名空间污染与 IIFE 总是将代码包裹成一个 IIFE(Immediately-Invoked Function Expression),用以创建独立隔绝的定义域.这一举措可防止全局命名空间被污染. IIFE 还可确保你的代码不会轻易被其它全局命名空间里的代码所修改(i.e. 第三方库,window 引用,被覆盖的未定义的关键字等等). 不推荐 var x = 10, y = 100; // Declaring variables in the global scope is result…
Introduction Surprisingly, a topic of named function expressions doesn't seem to be covered well enough on the web. This is probably why there are so many misconceptions floating around. In this article, I'll try to summarize both - theoretical and p…
Arrow Function.md Arrow Functions The basic syntax of an arrow function is as follows var fn = data => data; The code means : var fn = function( data ) { return data; } let getNumber = () => 42; console.log(typeof getNumber); console.log(getNumber()…
+function ($) { "use strict"; }(window.jQuery); 怎么理解? 匿名函数闭包 我们先来理一理函数表达式和函数声明的区别 函数表达式: 函数可以是匿名函数,也可以有函数名,但是这种函数无法直接使用,只有通过表达式左侧的变量来调用. var a = function(){ alert('Function expression'); } var b = new a(); 函数声明:必需要有函数名 function a(){ alert('Func…
An arrow function expression has a shorter syntax than a function expression and does not have its own this, arguments, super, or new.target. These function expressions are best suited for non-method functions, and they cannot be used as constructors…
Variable hoisting Another unusual thing about variables in JavaScript is that you can refer to a variable declared later, without getting an exception. This concept is known as hoisting; variables in JavaScript are in a sense "hoisted" or lifted…
Introduction 本系列文章为You Don't Know JS的读书笔记. 书籍地址:https://github.com/getify/You-Dont-Know-JS Scope From Functions 一个非常普遍的观点是,Javascript的作用域是基于函数的,这个观点其实并不是那么正确,不过,让我们来先看一下函数级别的作用域. function foo(a) { var b = 2; // some code function bar() { // ... } //…
JS中常见的三种函数声明(statement)方式有这三种: // 函数表达式(function expression) var h = function () { // h } // 函数声明(function declaration) function h() { // h } // 构造函数(function constructor)function H() { // H } 先说三者的显著区别: 第一种声明方式也就是var声明方式,函数表达式,又叫做函数字面量(Function Lite…
