javascript常用函数（1）

文章主要内容列表：
1、  调整图片大小，不走形（FF IE 兼容）/ 剪切图片（overflow:hidden） 2、  控制textarea区域文字数量 3、  点击显示新窗口 4、  input框自动随内容自动变长 5、  添加收藏夹 6、  设置首页 7、  Jquery + Ajax 判断用户是否存在 8、  判断email格式是否正确 9、  综合判断用户名（长度，英文字段等） 10、新闻滚动 11、 只允许输入正整数 （shopping cart 使用） 或者 正数 （正整数和正小数） 12、 转换字符串为数字 13、 判断文件格式（获得文件后缀） 14、 截取字符串 15、分割字符串
主要内容 ： 1、 调整图片大小，不走形（FF IE 兼容）


// 用法 <img src="this_image_path.jpg" onload="DrawImage(this,450,450);" />
function DrawImage(ImgD,FitWidth,FitHeight){
var image=new Image();
image.src=ImgD.src;
if(image.width>0 && image.height>0){
if(image.width/image.height>= FitWidth/FitHeight){
if(image.width>FitWidth){
ImgD.width=FitWidth;
ImgD.height=(image.height*FitWidth)/image.width;
}else{
ImgD.width=image.width;
ImgD.height=image.height;
}
} else{
if(image.height>FitHeight){
ImgD.height=FitHeight;
ImgD.width=(image.width*FitHeight)/image.height;
}else{
ImgD.width=image.width;
ImgD.height=image.height;
}
}
}
}

通过 overflow：hidden进行剪切：


function clipImage(o, w, h){
var img = new Image();
img.src = o.src;
if(img.width >0 && img.height>0)
{
if(img.width/img.height >= w/h)
{
if(img.width > w)
{
o.width = (img.width*h)/img.height;
o.height = h;
//o.setAttribute("style", "marginLeft:-" + ((o.width-w)/2).toString() + "px");
$(o).css("margin-left", "-"+((o.width-w)/2).toString() + "px");
}
else
{
o.width = img.width;
o.height = img.height;
}
}
else
{
if(img.height > h)
{
o.height = (img.height*w)/img.width;
o.width = w;
//o.setAttribute("style", "margin-top:-" + ((o.height-h)/2).toString() + "px");
//$(o).css("style", "margin-top:-" + ((o.height-h)/2).toString() + "px");
$(o).css("margin-top", "-"+((o.height-h)/2).toString() + "px");
}
else
{
o.width = img.width;
o.height = img.height;
}
}
}
}


实例：


<style type="text/css">
ul{list-style:none;}
ul li{float:left;padding:1px;border:#ccc 1px solid;width:120px;height:120px;overflow:hidden;text-align:center;over-flow:hidden;}
</style>
<ul>
<li><img src="1.jpg" onload="DrawImage(this,120,120);" /></li>
<li><img src="2.jpg" onload="clipImage(this,120,120);" /></li>
</ul>


2、控制textarea区域文字数量


<script>
/**
* Calculate how many characters remain in a textarea (jQuery)
* @param string textarea
* @param int maxLength
* @param string div
*/
function charsRemain(textarea, maxLength, div) {
var currentLength = $(textarea).val().length;

var charsLeft = maxLength - currentLength;
if (charsLeft < 0) { charsLeft = 0; }

$("#"+ div +"_charsRemain").html(charsLeft);

if (currentLength > maxLength) {
var fullText = $(textarea).val().substring(0, maxLength);
$(textarea).val(fullText);
}
}

/**
* Calculate how many characters remain in a textarea (javascript)
* @param string textarea
* @param int maxLength
* @param string div
*/
function charsRemain(textarea, maxLength, div) {
var currentLength = textarea.value.length;

var charsLeft = maxLength - currentLength;
if (charsLeft < 0) { charsLeft = 0; }

document.getElementById(div +"_charsRemain").innerHTML = charsLeft;

if (currentLength > maxLength) {
var fullText = textarea.value.substring(0, maxLength);
textarea.value = fullText;
}
}
</script>

<textarea rows="5" cols="15" onkeyup="charsRemain(this, 250, 'textarea');"></textarea>

<span id="textarea_charsRemain">250</span> characters remaining


3、点击显示新窗口


//弹窗
function g_OpenWindow(pageURL, innerWidth, innerHeight)
{
var ScreenWidth = screen.availWidth
var ScreenHeight = screen.availHeight
var StartX = (ScreenWidth - innerWidth) / 2
var StartY = (ScreenHeight - innerHeight) / 2
var wins = window.open(pageURL, 'OpenWin', 'left='+ StartX + ', top='+ StartY + ', Width=' + innerWidth +', height=' + innerHeight + ', resizable=yes, scrollbars=yes, status=no, toolbar=no, menubar=no, location=no')
wins.focus();
}


Java代码 ：


<script language="JavaScript">
// 自动弹出窗口
var whatsNew = open('','_blank','top=50,left=50,width=200,height=300,' + 'menubar=no,toolbar=no,directories=no,location=no,' + 'status=no,resizable=no,scrollbars=yes');
whatsNew.document.write('<center><b>news</b>< /center>');
whatsNew.document.write('<p>this is a test');
whatsNew.document.write('<p>deos address');
whatsNew.document.write('<p align="right">' + '<a href="javascript:self.close()">Close</a>');
whatsNew.document.close();
</script>


不幸的是，很多浏览器会屏蔽弹出窗口，你需要手动允许后方可看到！下面是强制弹出窗口，原理就是创建一个form，通过post打开。


<script language="javascript">
function ForceWindow (){
this.r = document.documentElement;
this.f = document.createElement("FORM");
this.f.target = "_blank";
this.f.method = "post";
this.r.insertBefore(this.f, this.r.childNodes[0]); //XML DOM : insertBefore() 方法可在已有的子节点前插入一个新的子节点。 insertBefore(newchild,refchild)
}

ForceWindow.prototype.pop = function (sUrl){
this.f.action = sUrl;
this.f.submit();
}

window.force = new ForceWindow();
</script>

<body onLoad="window.force.pop('http://deographics.com/')">
<div>
this is a test ! we will open the deographics's website~~
</div>
</body>


当然还有更好的办法就是


<script>
function openWin(){
window.showModalDialog(url,window, "help:no;scroll:no;resizable:no;status:0;dialogWidth:420px;dialogHeight:200px;center:yes");
}
</script>

 4、input框自动随内容自动变长


// input auto length
// <input name="words" size="2" maxlength="100" onkeyup="checkLength(this)"/><span id="char">0</span>

function checkLength(which) {
var maxchar=100;
//var oTextCount = document.getElementById("char");
iCount = which.value.replace(/[^u0000-u00ff]/g,"aa").length;
if(iCount<=maxchar){
//oTextCount.innerHTML = "<font color=#FF0000>"+ iCount+"</font>";
which.style.border = '1px dotted #FF0000';
which.size=iCount+2;
}else{
alert('Please input letter less than '+ maxchar);
}
}


5、添加收藏夹


// addfavorite
function addfavorite(){
if (document.all){
window.external.addFavorite('http://deographics.com/','deographics');
}else if (window.sidebar){
window.sidebar.addPanel('deographics', 'http://deographics.com/', "");
}
}


 6、设置首页


// setHomepage
function setHomepage(){
if(document.all){
document.body.style.behavior = 'url(#default#homepage)';
document.body.setHomePage('http://deographics.com/');
}else if(window.sidebar){
if(window.netscape){
try{
netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
}catch(e){
alert(" The operation was refused by browser,if you want to enable this feature, please enter in the address column 'about:config', then, change 'signed.applets.codebase_principal_support' to 'true' ");
}
}
var prefs = Components.classes['@mozilla.org/preferences-service;1'].getService(Components.interfaces.nsIPrefBranch);
prefs.setCharPref('browser.startup.homepage','http://deographics.com/');
}
}

7、Jquery + Ajax 判断用户是否存在


// 检测 用户名是否存在
$("#username").blur(function(){
var name = $(this).val(); var table = $(this).attr('title');
if(name!=''){
var dataString = 'username='+ name + '&table=' + table;
$.post("operate.php",dataString,function(data){ //alert(data);
if(data==0){
alert('This username already exist !'); $(this).val('').focus(); return false;
}
});
}
});


或者


var datastring = 'id=' + $id + '&pos=' + $pos;
$.ajax({
type: "POST",
url: url,
data: dataString,
beforeSend: function(){},
error: function(){alert('Send Error !');},
success: function(data) {
// do something
}
});


8、判断email格式是否正确


function chekemail(temail){
var pattern = /^[w]{1}[w.-_]*@[w]{1}[w-_.]*.[w]{2,4}$/i;
if(pattern.test(temail)){return true;}else{return false;}
}

 9、综合判断用户名（长度，英文字段等）


// 实例
var username = $('#username');
var backValue = VerifyInput('username');

if(backValue == 'length'){
alert("Username is make up of 3 - 15 characters!");
username.focus();
return false;
}else if(backValue == 'first'){
alert("the First character must be letter or number !");
username.focus();
return false;
}else if(backValue == 'back'){
alert("Username only contains letter number or '_' ");
username.focus();
return false;
}
// 判断
function VerifyInput(user){
var strUserID = $('#'+user).val();
if (strUserID.length < 3 || strUserID.length > 15){
return 'length';
}else{
for (nIndex=0; nIndex<strUserID.length; nIndex++){
cCheck = strUserID.charAt(nIndex);
if ( nIndex==0 && ( cCheck =='-' || cCheck =='_') ){
return 'first';
}
if (!(IsDigit(cCheck) || IsAlpha(cCheck) || cCheck=='-' || cCheck=='_' )){
return 'back';
}
}
}
}
function IsDigit(cCheck) {return (('0'<=cCheck) && (cCheck<='9'));}
function IsAlpha(cCheck) {return ((('a'<=cCheck) && (cCheck<='z')) || (('A'<=cCheck) && (cCheck<='Z')))}


10、新闻滚动


<style type="text/css">
ul,li{margin:0;padding:0;font-size:12px;color:#999;}
ul{height:100px;overflow:hidden;}
ul li{line-height:20px;height:20px;}
</style>

<ul id="news">
<li>New York web design Inc.1</li>
<li>Your site will be structured 2</li>
<li>hat will communicate the 3</li>

<li>hat will communicate the 4</li>
<li>hat will communicate the 5</li>
<li>hat will communicate the 6</li>
<li>hat will communicate the 7</li>
<li>hat will communicate the 8</li>
<li>hat will communicate the 9</li>

<li>New York web design Inc. 10</li>
<li>New York web design Inc.11</li>
<li>New York web design Inc. 12</li>
<li>New York web design Inc. 13</li>
<li>New York web design Inc. 14</li>
</ul>

Java代码 


// 用法 : 四个参数分别是:操作对象， 停留时间，相对速度（越小越快）,每次滚动多少(最好和Li的Line-height一致)。

scroll('news', 3000, 1, 20 );

function scroll(element, delay, speed, lineHeight) {
var numpergroup = 5;
var slideBox = (typeof element == 'string')?document.getElementById(element):element;
var delay = delay||1000;
var speed=speed||20;
var lineHeight = lineHeight||20;
var tid = null, pause = false;
var liLength = slideBox.getElementsByTagName('li').length;
var lack = numpergroup-liLength%numpergroup;
for(i=0;i<lack;i++){
slideBox.appendChild(document.createElement("li"));
}
var start = function() {
tid=setInterval(slide, speed);
}
var slide = function() {
if (pause) return;
slideBox.scrollTop += 2;
if ( slideBox.scrollTop % lineHeight == 0 ) {
clearInterval(tid);
for(i=0;i<numpergroup;i++){
slideBox.appendChild(slideBox.getElementsByTagName('li')[0]);
}
slideBox.scrollTop = 0;
setTimeout(start, delay);
}
}
slideBox.onmouseover=function(){pause=true;}
slideBox.onmouseout=function(){pause=false;}
setTimeout(start, delay);
}


11、只允许输入正整数 （shopping cart 使用）


<script language="JavaScript" type="text/javascript">
function checkNum(obj){
var re = /^[1-9]d*$/;
if (!re.test(obj.value)){
alert("只允许正整数!");
obj.value='';
obj.focus();
return false;
}
}
</script>

<input name="rate" type="text"onkeyup="checkNum(this)" />

 或正数


<script language="JavaScript" type="text/javascript">
function clearNoNum(obj)
{
//先把非数字的都替换掉，除了数字和.
objobj.value = obj.value.replace(/[^d.]/g,"");
//必须保证第一个为数字而不是.
objobj.value = obj.value.replace(/^./g,"");
//保证只有出现一个.而没有多个.
objobj.value = obj.value.replace(/.{2,}/g,".");
//保证.只出现一次，而不能出现两次以上
objobj.value = obj.value.replace(".","$#$").replace(/./g,"").replace("$#$",".");
}
</script>


只能输入数字和小数点的文本框：<input id="input1" onkeyup="clearNoNum(this)">   12、 转换字符串为数字


/*
js提供了parseInt()和parseFloat()两个转换函数。前者把值转换成整数，后者把值转换成浮点数。只有对String类型调用这些方法，这两个函数才能正确运行；对其他类型返回的都是NaN(Not a Number)。
*/

parseInt("1234blue"); //returns 1234
parseInt("0xA"); //returns 10
parseInt("22.5"); //returns 22
parseInt("blue"); //returns NaN

parseFloat("1234blue"); //returns 1234.0
parseFloat("0xA"); //returns NaN
parseFloat("22.5"); //returns 22.5
parseFloat("22.34.5"); //returns 22.34
parseFloat("0908"); //returns 908
parseFloat("blue"); //returns NaN

/*
还可使用强制类型转换（type casting）处理转换值的类型。使用强制类型转换可以访问特定的值，即使它是另一种类型的。
Boolean(value)——把给定的值转换成Boolean型；
Number(value)——把给定的值转换成数字（可以是整数或浮点数）；
String(value)——把给定的值转换成字符串。
*/

Boolean(""); //false – empty string
Boolean("hi"); //true – non-empty string
Boolean(100); //true – non-zero number
Boolean(null); //false - null
Boolean(0); //false - zero
Boolean(new Object()); //true – object

Number(false) 0
Number(true) 1
Number(undefined) NaN
Number(null) 0
Number( "5.5 ") 5.5
Number( "56 ") 56
Number( "5.6.7 ") NaN
Number(new Object()) NaN
Number(100) 100

var s1 = String(null); //"null"
var oNull = null;
var s2 = oNull.toString(); //won't work, causes an error

 13、 判断文件格式（获得文件后缀）


// 用法：get_ext(this,'img');

function get_ext(name){
var pos = name.lastIndexOf('.');
var extname = name.substring(pos,name.length) // like: str.split('.')
var lastname = extname.toLowerCase();

if (lastname !='.jpg' && lastname !='.gif' && lastname !='.png' && lastname !='.bmp'){
return lastname;
}else{
return name;
}
}
}


14、截取字符串


// 简单型

<script type="text/javascript">

var str="Hello world!"
document.write(str.substr(3,7))

</script>

// 结果是 lo worl


// 复杂型（中文或者中英文混合截取）

<script>
//截取字符串 包含中文处理
//(串,长度,增加...)
function subString(str, len, hasDot)
{
var newLength = 0;
var newStr = "";
var chineseRegex = /[^x00-xff]/g;
var singleChar = "";
var strLength = str.replace(chineseRegex,"**").length;
for(var i = 0;i < strLength;i++)
{
singleChar = str.charAt(i).toString();
if(singleChar.match(chineseRegex) != null)
{
newLength += 2;
}
else
{
newLength++;
}
if(newLength > len)
{
break;
}
newStr += singleChar;
}

if(hasDot && strLength > len)
{
newStr += "...";
}
return newStr;
}

document.write(subString("你好，this is a test!",10,1)); // 参数依次为 字符串， 截取的长度 和 是否显示省略号
</script>

15、分割字符串


<script type="text/javascript">

var str = 'this_is_a_test_!';
var arr = str.split('_');

document.write(arr + "<br />"); // 罗列全部
document.write(arr[0] + "<br />"); // 取单项

</script>


 以上就是小编为大家整理的常用的javascript函数，希望对大家的学习有所帮助，之后还有更多javascript常用函数分享给大家，继续关注。


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