<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>Document</title> <style> div { width: 600px; margin: 100px auto; } .message { display: inline-block; font-size: 12px; color: #999; background: url(images/mess.png) no-repeat left center; padding-left: 20px; } .wrong { color: red; background-image: url(images/wrong.png); } .right { color: green; background-image: url(images/right.png); } </style> </head> <body> <div class="register"> <input type="password" class="ipt"> <p class="message">请输入6~16位密码</p> </div> <script> //获取事件 var ipt = document.querySelector('.ipt'); var message = document.querySelector('.message'); //2. 注册事件 失去焦点 ipt.onblur = function() { // 根据表单里面值的长度 ipt.value.length if (this.value.length < 6 || this.value.length > 16) { // 当输入的值不满足条件的时候，增加一个wrong的类名样式，message需要保留 message.className = 'message wrong'; message.innerHTML = '您输入的位数不对要求6~16位'; } else { message.className = 'message right'; message.innerHTML = '您输入的正确'; } } </script> </body> </html>
