基础版
从我们平时上网的经验来看,验证码一般是四位,由数字和字母组成。 那么接下来楼主将带领大家一步步用JavaScript做出一个验证码脚本! 先给出成品，方便大家理解：
1.既然是四位验证码,我们的思路就要打开一些了,首先我们需要一个数组来储存字母和数字。
2.然后我们需要让它随机显示数组中的元素，这里我们建立一个codeNumber变量来随机显示的数字,但我们需要的是四位验证码，而现在数组中的元素都是单个的，怎么办呢？简单！我们再建立一个securityCode变量来储存数组中的元素不就得了。代码如下：
可以看出此时securityNumber变量储存的就是一个四位随机验证码 3.好了，经过简单的两步，我们就得到了四位验证码。我们将它放在一个createCode函数中。
4.接下来我们创建一个验证机制：
5.小小修饰下验证码：
进阶：进一步阻止机器人的高级技巧
接触的大部分项目中，验证码一直都是后台干的事，这两天正好有一个页面需要验证码，第时间想着后台实现，但突然转念一想大部分项目貌似对安全性要求不是很高，又要求有点阻止机器人的技巧，于是就用前端写了一个验证码。并利用CSS3的transform属性里的rotate设置旋转，再随机弄点干扰线，最后为了在所有DOM节点的上边加一层opacity=0的DIV，一个前端验证码就出来了。
vCode代码：
str : [
'a','b','c','d','e','f','g','h','i','j','k','l','m','o','p','q','r','s','t','x','u','v','y','z','w','n','0','1','2','3','4','5','6','7','8','9'
],randint : function(n,m){
var c = m-n+1;
var num = Math.random() * c + n;
return Math.floor(num);
},randStr : function(){
var _this = this;
var leng = _this.str.length - 1;
var randkey = _this.randint(0,leng);
return _this.str[randkey];
},create : function(len){
var _this = this;
var l = len || 10;
var str = '';
for(var i = 0 ; i<l ; i++){
str += _this.randStr();
}
return str;
}
};
length = length ? length : 10;
return key.create(length);
};
var randint = function(n,m){
var c = m-n+1;
var num = Math.random() * c + n;
return Math.floor(num);
};
var vCode = function(dom,options){
this.codeDoms = [];
this.lineDoms = [];
this.initOptions(options);
this.dom = dom;
this.init();
this.addEvent();
this.update();
this.mask();
};
vCode.prototype.init = function(){
this.dom.style.position = "relative";
this.dom.style.overflow = "hidden";
this.dom.style.cursor = "pointer";
this.dom.title = "点击更换验证码";
this.dom.style.background = this.options.bgColor;
this.w = this.dom.clientWidth;
this.h = this.dom.clientHeight;
this.uW = this.w / this.options.len;
};
vCode.prototype.mask = function(){
var dom = document.createElement("div");
dom.style.cssText = [
"width: 100%","height: 100%","left: 0","top: 0","position: absolute","cursor: pointer","z-index: 9999999"
].join(";");
dom.title = "点击更换验证码";
this.dom.appendChild(dom);};
vCode.prototype.addEvent = function(){
var _this = this;
_this.dom.addEventListener("click",function(){
_this.update.call(_this);
});
};
vCode.prototype.initOptions = function(options){
var f = function(){
this.len = 4;
this.fontSizeMin = 20;
this.fontSizeMax = 48;
this.colors = [
"green","red","blue","#53da33","#AA0000","#FFBB00"
];
this.bgColor = "#FFF";
this.fonts = [
"Times New Roman","Georgia","Serif","sans-serif","arial","tahoma","Hiragino Sans GB"
];
this.lines = 8;
this.lineColors = [
"#888888","#FF7744","#888800","#008888"
];
this.lineHeightMin = 1;
this.lineHeightMax = 3;
this.lineWidthMin = 1;
this.lineWidthMax = 60;
};
this.options = new f();
if(typeof options === "object"){
for(i in options){
this.options[i] = options[i];
}
}};
vCode.prototype.update = function(){
for(var i=0; i<this.codeDoms.length; i++){
this.dom.removeChild(this.codeDoms[i]);
}
for(var i=0; i<this.lineDoms.length; i++){
this.dom.removeChild(this.lineDoms[i]);
}
this.createCode();
this.draw();
};
vCode.prototype.createCode = function(){
this.code = randstr(this.options.len);
};
vCode.prototype.verify = function(code){
return this.code === code;
};
vCode.prototype.draw = function(){
this.codeDoms = [];
for(var i=0; i<this.code.length; i++){
this.codeDoms.push(this.drawCode(this.code[i],i));
}
this.drawLines();};
vCode.prototype.drawCode = function(code,index){
var dom = document.createElement("span");
dom.style.cssText = [
"font-size:" + randint(this.options.fontSizeMin,this.options.fontSizeMax) + "px","color:" + this.options.colors[randint(0,this.options.colors.length - 1)],"left:" + randint(this.uW * index,this.uW * index + this.uW - 10) + "px","top:" + randint(0,this.h - 30) + "px","transform:rotate(" + randint(-30,30) + "deg)","-ms-transform:rotate(" + randint(-30,"-moz-transform:rotate(" + randint(-30,"-webkit-transform:rotate(" + randint(-30,"-o-transform:rotate(" + randint(-30,"font-family:" + this.options.fonts[randint(0,this.options.fonts.length - 1)],"font-weight:" + randint(400,900)
].join(";");
dom.innerHTML = code;
this.dom.appendChild(dom);
return dom;};
vCode.prototype.drawLines = function(){
this.lineDoms = [];
for(var i=0; i<this.options.lines; i++){
var dom = document.createElement("div");
dom.style.cssText = [
"position: absolute","opacity: " + randint(3,8) / 10,"width:" + randint(this.options.lineWidthMin,this.options.lineWidthMax) + "px","height:" + randint(this.options.lineHeightMin,this.options.lineHeightMax) + "px","background: " + this.options.lineColors[randint(0,this.options.lineColors.length - 1)],"left:" + randint(0,this.w - 20) + "px",this.h) + "px",900)
].join(";");
this.dom.appendChild(dom);
this.lineDoms.push(dom);
}};
this.vCode = vCode;
}).call(this);
用法：
