js实现简单的验证码

验证码大家应该不陌生，主要是为了网站的安全性，防止恶意注册和登陆。验证码实现的方式各有不同，下面是一段用javascript实现的验证码效果，供大家参考之用，希望能够给大家带来帮助。
运行效果图：

代码如下：

<html><head><title>js验证码</title><style type="text/css">.code { background:url（code_bg.jpg）; font-family:Arial; font-style:italic; color:blue; font-size:30px; border:0; padding:2px 3px; letter-spacing:3px; font-weight:bolder; float:left; cursor:pointer; width:150px; height:60px; line-height:60px; text-align:center; vertical-align:middle;}a { text-decoration:none; font-size:12px; color:#288bc4;}a:hover { text-decoration:underline;}</style><script type="text/javascript">var code;function createCode（） { code = ""; var codeLength = 6; //验证码的长度 var checkCode = document.getElementById（"checkCode"）; var codeChars = new Array（0, 1, 2, 3, 4, 5, 6, 7, 8, 9, "a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"）; //所有候选组成验证码的字符，当然也可以用中文的 for（var i = 0; i < codeLength; i++）{var charNum = Math.floor（Math.random（） * 52）;code += codeChars[charNum]; } if（checkCode）{checkCode.className = "code";checkCode.innerHTML = code; }}function validateCode（） { var inputCode=document.getElementById（"inputCode"）.value; if（inputCode.length <= 0）{alert（"请输入验证码！"）; } else if（inputCode.toUpperCase（） ！= code.toUpperCase（））{ alert（"验证码输入有误！"）; createCode（）; } else{alert（"验证码正确！"）; }}</script></head><body onload="createCode（）"><form id="form1" runat="server" onsubmit="validateCode（）"> <div><table border="0" cellspacing="5" cellpadding="5" > <tr><td></td><td><div class="code" id="checkCode" onclick="createCode（）" ></div></td><td><a href="#" onclick="createCode（）">看不清换一张</a></td> </tr> <tr><td>验证码：</td><td><input style="float:left;" type="text"id="inputCode" /></td><td>请输入验证码</td> </tr> <tr><td></td><td><input id="Button1" onclick="validateCode（）;" type="button" value="确定" /></td><td></td> </tr></table> </div></form></body></html>

希望本文所述对大家学习javascript程序设计有所帮助。