JavaScript Patterns 4.7 Init-Time Branching
When you know that a certain condition will not change throughout the life of the program, it makes sense to test the condition only once. Browser sniffing (or feature detection) is a typical example.
// BEFORE
var utils = {
addListener : function(el, type, fn) {
if ( typeof window.addEventListener === 'function') {
el.addEventListener(type, fn, false);
} else if ( typeof document.attachEvent === 'function') {// IE
el.attachEvent('on' + type, fn);
} else {// older browsers
el['on' + type] = fn;
}
},
removeListener : function(el, type, fn) {
// pretty much the same...
}
};
// AFTER
// the interface
var utils = {
addListener : null,
removeListener : null
};
// the implementation
if ( typeof window.addEventListener === 'function') {
utils.addListener = function(el, type, fn) {
el.addEventListener(type, fn, false);
};
utils.removeListener = function(el, type, fn) {
el.removeEventListener(type, fn, false);
};
} else if ( typeof document.attachEvent === 'function') {// IE
utils.addListener = function(el, type, fn) {
el.attachEvent('on' + type, fn);
};
utils.removeListener = function(el, type, fn) {
el.detachEvent('on' + type, fn);
};
} else {// older browsers
utils.addListener = function(el, type, fn) {
el['on' + type] = fn;
};
utils.removeListener = function(el, type, fn) {
el['on' + type] = null;
};
}
References:
JavaScript Patterns - by Stoyan Stefanov (O`Reilly)
JavaScript Patterns 4.7 Init-Time Branching的更多相关文章
- JavaScript Patterns 5.4 Module Pattern
MYAPP.namespace('MYAPP.utilities.array'); MYAPP.utilities.array = (function () { // dependencies var ...
- JavaScript Patterns 7.1 Singleton
7.1 Singleton The idea of the singleton pattern is to have only one instance of a specific class. Th ...
- JavaScript Patterns 6.7 Borrowing Methods
Scenario You want to use just the methods you like, without inheriting all the other methods that yo ...
- JavaScript Patterns 6.6 Mix-ins
Loop through arguments and copy every property of every object passed to the function. And the resul ...
- JavaScript Patterns 6.5 Inheritance by Copying Properties
Shallow copy pattern function extend(parent, child) { var i; child = child || {}; for (i in parent) ...
- JavaScript Patterns 6.4 Prototypal Inheritance
No classes involved; Objects inherit from other objects. Use an empty temporary constructor function ...
- JavaScript Patterns 6.3 Klass
Commonalities • There’s a convention on how to name a method, which is to be considered the construc ...
- JavaScript Patterns 6.2 Expected Outcome When Using Classical Inheritance
// the parent constructor function Parent(name) { this.name = name || 'Adam'; } // adding functional ...
- JavaScript Patterns 6.1 Classical Versus Modern Inheritance Patterns
In Java you could do something like: Person adam = new Person(); In JavaScript you would do: var ada ...
随机推荐
- sqlite3存储格式
本篇介绍sqlite3数据库文件的存储格式.通过阅读源读源代码可以知道sqlite的设计思想.一个sqlite数据库文件对应着一个数据库.sqlite将数据库文件划分大小一致的存储(以区分内存)页面, ...
- Java魔法堂：以Windows服务的形式运行Java程序
一.前言 由于防止维护人员误操作关闭Java控制台程序,因此决定将其改造为以Windows服务的形式运行.弄了一个上午总算搞定了,下面记录下来,以供日后查阅. 二.Java Service Wrapp ...
- 剑指offer面试题30：最小的k个数
一.题目描述 输入n个整数,找出其中最小的K个数.例如输入4,5,1,6,2,7,3,8这8个数字,则最小的4个数字是1,2,3,4,. 二.解题思路 1.思路1 首先对数组进行排序,然后取出前k个数 ...
- How to manage the certificates in the PC
1.open Run command. 2.enter 'mmc' . 3.Click File, and Add or Remove Snap-in. 4.Select Certificates, ...
- Servelet面试题
1. Servlet与JSP有什么区别? Servlet和JSP完成的功能是相同的,都可以接收用户的请求,可以对用户进行响应,可以调用业务方法. 不同点在于JSP是在html或者xml中嵌入了Java ...
- jQuery实现隐藏标签
要求:用户进入该页面时,品牌列表默认是精简显示,用户可以单击商品列表下方的“显示全部品牌”按钮来显示全部的品牌. <%@ Page Language="C#" Inherit ...
- ViewData和TempData以及Session的小结
ViewData一般用在从控制器向页面上传递数据. Public ActionResult Show() { ViewData["message"]="你好"; ...
- Verilog学习笔记设计和验证篇（一）...............总线和流水线
总线 总线是运算部件之间数据流通的公共通道.在硬线逻辑构成的运算电路中只要电路的规模允许可以比较自由的确定总线的位宽,从而大大的提高数据流通的速度.各个运算部件和数据寄存器组可以通过带有控制端的三态门 ...
- 【GPU编解码】GPU硬解码---CUVID
问题描述:项目中,需要对高清监控视频分析处理,经测试,其解码过程所占CPU资源较多,导致整个系统处理效率不高,解码成为系统的瓶颈. 解决思路: 利用GPU解码高清视频,降低解码所占用CPU资源,加速解 ...
- Android 手机卫士14--Widget窗口小部件AppWidgetProvider
1.AndroidManifest.xml根据窗体小部件广播接受者关键字android.appwidget.action.APPWIDGET_UPDATE 搜索android:resource=&qu ...