JavaScript ID card number verification function (can distinguish authenticity, supports 15 or 18-digit ID number) test error is 0_javascript skills

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The more direct test code is :
alert(test("ID card number"));
After testing, the above JS verification is too powerful. After entering the correct ID card, an error will be reported if I change any one! It is very practical. It will be easy for everyone to know whether the ID card entered by the user is correct or not. <script> //验证身份证号方法 var test=function(idcard){ var Errors=new Array("验证通过!","身份证号码位数不对!","身份证号码出生日期超出范围或含有非法字符!","身份证号码校验错误!","身份证地区非法!"); var area={11:"北京",12:"天津",13:"河北",14:"山西",15:"内蒙古",21:"辽宁",22:"吉林",23:"黑龙江",31:"上海",32:"江苏",33:"浙江",34:"安徽",35:"福建",36:"江西",37:"山东",41:"河南",42:"湖北",43:"湖南",44:"广东",45:"广西",46:"海南",50:"重庆",51:"四川",52:"贵州",53:"云南",54:"西藏",61:"陕西",62:"甘肃",63:"青海",64:"宁夏",65:"xinjiang",71:"台湾",81:"香港",82:"澳门",91:"国外"} var idcard,Y,JYM; var S,M; var idcard_array = new Array(); idcard_array = idcard.split(""); if(area[parseInt(idcard.substr(0,2))]==null) return Errors[4]; switch(idcard.length){ case 15: if ((parseInt(idcard.substr(6,2))+1900) % 4 == 0 || ((parseInt(idcard.substr(6,2))+1900) % 100 == 0 && (parseInt(idcard.substr(6,2))+1900) % 4 == 0 )){ ereg = /^[1-9][0-9]{5}[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|[1-2][0-9]))[0-9]{3}$/;//测试出生日期的合法性 } else{ ereg = /^[1-9][0-9]{5}[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|1[0-9]|2[0-8]))[0-9]{3}$/;//测试出生日期的合法性 } if(ereg.test(idcard)) return Errors[0]; else return Errors[2]; break; case 18: if( parseInt(idcard.substr(6,4)) % 4 == 0 || ( parseInt(idcard.substr(6,4)) % 100 == 0 && parseInt(idcard.substr(6,4))%4 == 0 )){ ereg = /^[1-9][0-9]{5}19[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|[1-2][0-9]))[0-9]{3}[0-9Xx]$/;//闰年出生日期的合法性正则表达式 } else{ ereg = /^[1-9][0-9]{5}19[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|1[0-9]|2[0-8]))[0-9]{3}[0-9Xx]$/;//平年出生日期的合法性正则表达式 } if(ereg.test(idcard)){ S = (parseInt(idcard_array[0]) + parseInt(idcard_array[10])) * 7 + (parseInt(idcard_array[1]) + parseInt(idcard_array[11])) * 9 + (parseInt(idcard_array[2]) + parseInt(idcard_array[12])) * 10 + (parseInt(idcard_array[3]) + parseInt(idcard_array[13])) * 5 + (parseInt(idcard_array[4]) + parseInt(idcard_array[14])) * 8 + (parseInt(idcard_array[5]) + parseInt(idcard_array[15])) * 4 + (parseInt(idcard_array[6]) + parseInt(idcard_array[16])) * 2 + parseInt(idcard_array[7]) * 1 + parseInt(idcard_array[8]) * 6 + parseInt(idcard_array[9]) * 3 ; Y = S % 11; M = "F"; JYM = "10X98765432"; M = JYM.substr(Y,1); if(M == idcard_array[17]) return Errors[0]; else return Errors[3]; } else return Errors[2]; break; default: return Errors[1]; break; } } //测试代码 var theid=prompt("请输入身份证号码","15位或18位"); if(theid!=""){ document.write(test(theid)); }else{ //theid=prompt("请输入身份证号码","15位或18位"); } </script>