前言：
根据身份证号判断精确周岁年龄，可以精确到天，即周岁以生日当天为准，生日当天周岁+1，少一天则不加。
实现方法：
1 <!DOCTYPE html> 2 <html> 3 <head> 4 <meta charset="UTF-8"> 5 <title></title> 6 </head> 7 <body> 8 <script> 9 10 /** 11 * 根据身份证号，获取精缺周岁年龄 12 * @param {Object} strBirthday 生日格式：19880808 13 */ 14 function getAgeByPid(strBirthday){ 15 var birthYear = strBirthday.substr(0,4) 16 var birthMonth = strBirthday.substr(4,2) 17 var birthDay = strBirthday.substr(6,2) 18 19 d = new Date(); 20 var nowYear = d.getFullYear(); 21 var nowMonth = d.getMonth() + 1; 22 var nowDay = d.getDate(); 23 24 if(nowYear == birthYear) 25 { 26 returnAge = 0;//同年 则为0岁 27 } 28 else 29 { 30 var ageDiff = nowYear - birthYear ; //年之差 31 if(ageDiff > 0) 32 { 33 if(nowMonth == birthMonth) 34 { 35 var dayDiff = nowDay - birthDay;//日之差 36 if(dayDiff < 0) 37 { 38 returnAge = ageDiff - 1; 39 } 40 else 41 { 42 returnAge = ageDiff ; 43 } 44 } 45 else 46 { 47 var monthDiff = nowMonth - birthMonth;//月之差 48 if(monthDiff < 0) 49 { 50 returnAge = ageDiff - 1; 51 } 52 else 53 { 54 returnAge = ageDiff ; 55 } 56 } 57 } 58 else 59 { 60 returnAge = -1;//返回-1 表示出生日期输入错误 晚于今天 61 } 62 } 63 return returnAge;//返回周岁年龄 64 } 65 /** 66 * 获取年龄的单击事件 67 */ 68 function getAge(){ 69 var pid=document.getElementById("txtPid").value; 70 pid=pid.substr(6,8) 71 alert(getAgeByPid(pid)) 72 } 73 </script> 74 <input type="text" name="pid" id="txtPid"> 75 <input type="button" value="查询" id="btnGetAge" onclick="getAge()"> 76 </body> 77 </html>