这些年，我收集的JavaScript代码(二)
一、JavaScript跨平台事件
对于跨平台事件我们一般这么写(只例举添加事件)：
function addEventHandler(oTarget, sEventType, fnHandler){ if(oTarget.addEventListener){ oTarget.addEventListener(sEventType,fnHandler,false); } else if(oTarget.attachEvent){ oTarget.attachEvent("on"+sEventType,fnHandler); } else{ oTarget["on"+sEventType]=fnHandler; }}那么下面这段代码的效果是什么样的呢？
<div id="test">Test</div>...var oDiv=document.getElementById("test");addEventHandler(oDiv,"mouseover",function(){ alert("over "+this.id);});由于IE的this问题，在IE中果断地弹出了 over undefined，所以跨平台的事件更好的写法是这样的：
function addEventHandler(oTarget, sEventType, fnHandler){ if(oTarget.addEventListener){ oTarget.addEventListener(sEventType,fnHandler,false); } else if(oTarget.attachEvent){ oTarget.attachEvent("on"+sEventType,function(){ return fnHandler.call(oTarget,window.event); }); } else{ oTarget["on"+sEventType]=fnHandler; }}二、合并两个Array并去掉重复项
Array.prototype.unique = function() { var a = this.concat(); for(var i=0; i<a.length; ++i) { for(var j=i+1; j<a.length; ++j) { if(a[i] === a[j]) a.splice(j, 1); } } return a;};//Demovar array1 = ["a","b"];var array2 = ["b", "c"];var array3 = array1.concat(array2).unique();// ["a","b","c"]三、typeof === "undefined" vs. != null
if(typeof neverDeclared == "undefined") //no errorsif(neverDeclared == null) //throws ReferenceError: neverDeclared is not defined
so，typeof === "undefined" is better!
四、setTimeout(fn, 0)的意义
浏览器同时要做很多事，这些事情以队列的方式存在，执行JavaScript只是其中之一，setTimeout(fn, 0)表面上看是立即执行的意思，但实际上只是在浏览器事件队列中添加了一个新的事件，由于队列是先进先出，所以fn会等等到当前队列中的事件执行完后再执行。由于JavaScript的定时器回调函数是异步执行的，所以产生的效果就是等页面上同步事件(包括页面渲染与同步JS代码)执行完之后再执行。
一个简单的示例：
<script type="text/javascript"> //one document.getElementById("imgTest").style.borderBottom="5px solid #000"; //two setTimeout(function(){ document.getElementById("imgTest").style.borderBottom="5px solid #000"; }, 0);</script><img src="http://jscode.chinacxy.com/img_lib/m_400_600_01.jpg" id="imgTest" alt=""/>one会报错，因为页面执行到这里时还没有img，但two却可以。
五、增强版取URL中的参数
function getQueryString() { var result = {}, queryString = location.search.substring(1), re = /([^&=]+)=([^&]*)/g, m; while (m = re.exec(queryString)) { result[decodeURIComponent(m[1])] = decodeURIComponent(m[2]); } return result;}// demovar myParam = getQueryString()["myParam"];六、检查一个object是否是jQuery object
if(obj instanceof jQuery)
七、检查一个数是否为整数或浮点数
function isInt(n) { return typeof n === 'number' && n % 1 == 0;}// or ,this support ie3function isInt(n) { return typeof n === 'number' && parseFloat(n) == parseInt(n, 10) && !isNaN(n);}function isFloat (n) { return n===+n && n!==(n|0);}八、用JavaScript添加style节点
var css = 'h1 { background: red; }', head = document.getElementsByTagName('head')[0], style = document.createElement('style');style.type = 'text/css';if(style.styleSheet){ style.styleSheet.cssText = css;}else{ style.appendChild(document.createTextNode(css));}head.appendChild(style);九、如何跳出双重循环
function foo (){ dance: for(var k = 0; k < 4; k++){ for(var m = 0; m < 4; m++){ if(m == 2){ break dance; } } }}十、把一个Array追加到另一个Array上
var a=[1,2],b=[3,4,5];a.push.apply(a,b);/*a: [1, 2, 3, 4, 5]*/
十一、用jQuery把页面上的一个tag换成另一个tag
如把页面上所有的code换为pre：
<code> A </code><code> B </code><code> C </code>//change to<pre> A </pre><pre> A </pre><pre> A </pre>
jQuery代码：
$('code').contents().unwrap().wrap('<pre/>');//or$('code').replaceWith(function(){ return $("<pre />").append($(this).contents());});十二、取数组中的最小值和最大值
var arr = new Array();arr[0] = 100;arr[1] = 0;arr[2] = 50;var min = Math.min.apply(null, arr), max = Math.max.apply(null, arr);
十三、取两个数组交集
/* finds the intersection of * two arrays in a simple fashion. * * PARAMS * a - first array, must already be sorted * b - second array, must already be sorted * * NOTES * * Should have O(n) operations, where n is * n = MIN(a.length(), b.length()) */function arrayIntersection(a, b){ var ai=0, bi=0; var result = new Array(); while( ai < a.length && bi < b.length ) { if (a[ai] < b[bi] ){ ai++; } else if (a[ai] > b[bi] ){ bi++; } else /* they're equal */ { result.push(a[ai]); ai++; bi++; } } return result;}console.log(arrayIntersection([1,2,3],[2,3,4,5,6]));//[2,3]注释中已经说明了，传入的数组要已经排过序的。
十四、统计一个字符串中某段子串出现的次数
var temp = "This is a string.";var count = temp.match(/is/g);
十五、方法返回多个值
//Onevar mValues= function(){ var a ="a"; var b = "b"; return [a, b]; };var values= mValues();var valOne= values[0];var valTwo = values[1];//Twovar mValues= function(){ var a= "a"; var b = "b"; return { 'a': a, 'b': b }; };var values= mValues();var valOne= values.a;var valTwo = values.b;十六、Array迭代器
function createIterator(x) { var i = 0; return function(){ return x[i++]; };}var iterator=createIterator(['a','b','c','d','e','f','g']);var current;while(current=iterator()){ console.log(current);}注意，如果数组中有0、false、""、null、NaN迭代器将会停止。
十七、根据日计算年龄
function getAge(dateString) { var today = new Date(); var birthDate = new Date(dateString); var age = today.getFullYear() - birthDate.getFullYear(); var m = today.getMonth() - birthDate.getMonth(); if (m < 0 || (m === 0 && today.getDate() < birthDate.getDate())) { age--; } return age;}
console.log(getAge("2005,8,1"));//6十八、判断当前页面是否被放入了iframe中
if(self==top){ //not in iframe}else{ //in iframe}这段代码可以用来防止网页被放入iframe中，不过如果别人定义了self和top变量覆盖了浏览器默认值可能会失效。
十九、把arguments转换为Array
var args = Array.prototype.slice.call(arguments, 0);
二十、日期格式化
来源：javascript日期格式化函数，跟C#中的使用方法类似
Date.prototype.toString=function(format,loc){ var time={}; time.Year=this.getFullYear(); time.TYear=(""+time.Year).substr(2); time.Month=this.getMonth()+1; time.TMonth=time.Month<10?"0"+time.Month:time.Month; time.Day=this.getDate(); time.TDay=time.Day<10?"0"+time.Day:time.Day; time.Hour=this.getHours(); time.THour=time.Hour<10?"0"+time.Hour:time.Hour; time.hour=time.Hour<13?time.Hour:time.Hour-12; time.Thour=time.hour<10?"0"+time.hour:time.hour; time.Minute=this.getMinutes(); time.TMinute=time.Minute<10?"0"+time.Minute:time.Minute; time.Second=this.getSeconds(); time.TSecond=time.Second<10?"0"+time.Second:time.Second; time.Millisecond=this.getMilliseconds(); time.Week=this.getDay(); var MMMArrEn=["Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"]; var MMMArr=["一月","二月","三月","四月","五月","六月","七月","八月","九月","十月","十一月","十二月"]; var WeekArrEn=["Sun","Mon","Tue","Web","Thu","Fri","Sat"]; var WeekArr=["星期日","星期一","星期二","星期三","星期四","星期五","星期六"]; var oNumber=time.Millisecond/1000; if(format!=undefined && format.replace(/\s/g,"").length>0){ if(loc!=undefined && loc =="en"){ MMMArr=MMMArrEn.slice(0); WeekArr=WeekArrEn.slice(0); } format=format .replace(/yyyy/ig,time.Year) .replace(/yyy/ig,time.Year) .replace(/yy/ig,time.TYear) .replace(/y/ig,time.TYear) .replace(/MMM/g,MMMArr[time.Month-1]) .replace(/MM/g,time.TMonth) .replace(/M/g,time.Month) .replace(/dd/ig,time.TDay) .replace(/d/ig,time.Day) .replace(/HH/g,time.THour) .replace(/H/g,time.Hour) .replace(/hh/g,time.Thour) .replace(/h/g,time.hour) .replace(/mm/g,time.TMinute) .replace(/m/g,time.Minute) .replace(/ss/ig,time.TSecond) .replace(/s/ig,time.Second) .replace(/fff/ig,time.Millisecond) .replace(/ff/ig,oNumber.toFixed(2)*100) .replace(/f/ig,oNumber.toFixed(1)*10) .replace(/EEE/g,WeekArr[time.Week]); } else{ format=time.Year+"-"+time.Month+"-"+time.Day+" "+time.Hour+":"+time.Minute+":"+time.Second; } return format;}var d=new Date();console.log(d.toString()); //2012-7-27 9:26:52console.log(d.toString("")); //2012-7-27 9:26:52console.log(d.toString("yyyy-MM-dd HH:mm:ss")); //2012-07-27 09:26:52console.log(d.toString("yyyy年MM月dd日 HH:mm:ss")); //2012年07月27日 09:26:52console.log(d.toString("yyyy-MM-dd HH:mm:ss fff")); //2012-07-27 09:26:52 237console.log(d.toString("yyyy年 MMM dd EEE")); //2012年 七月 27 星期五console.log(d.toString("yyyy MMM dd EEE","en")); //2012 Jul 27 FriTAG:
