JS验证身份证的合法性

//验证身份证的合法性
function IdentityCodeValid(code) {
var city={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:"新疆",71:"台湾",81:"香港",82:"澳门",91:"国外 "};
var tip = "";
var pass= true;

if(!code || !/^\d{6}(18|19|20)?\d{2}(0[1-9]|1[12])(0[1-9]|[12]\d|3[01])\d{3}(\d|X)$/i.test(code)){
tip = "身份证号格式错误";
pass = false;
}
else if(!city[code.substr(0,2)]){
tip = "地址编码错误";
pass = false;
}
else{
//18位身份证须要验证最后一位校验位
if(code.length == 18){
code = code.split('');
//∑(ai×Wi)(mod 11)
//加权因子
var factor = [ 7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2 ];
//校验位
var parity = [ 1, 0, 'X', 9, 8, 7, 6, 5, 4, 3, 2 ];
var sum = 0;
var ai = 0;
var wi = 0;
for (var i = 0; i < 17; i++)
{
ai = code[i];
wi = factor[i];
sum += ai * wi;
}
var last = parity[sum % 11];
if(parity[sum % 11] != code[17]){
tip = "校验位错误";
pass =false;
}
}
}
return pass;
}