JavaScript ID card authenticity verification method

var IdCardValid = {//身份证检查
	isIdCard : function(_id) {
		var returnObj = new Object();
		var id = $.trim(_id.toUpperCase());
		var idArray = this._splitId(id);
		
		if (idArray.length > 0) {
			if (id.length != 18) {
				returnObj.status = false;
				returnObj.info = " 身份证号码必须是18位";

				return returnObj;
			}

			var checksum = id.substring(17, 18);
			var sum = 0;

			for ( var i = 1; i <= idArray.length; i++) {
				var Ai = idArray[i - 1];
				var Wi = this._getWeightingFactor(i);

				if (Wi != -1) {
					sum += Ai * Wi;
				}
			}

			var mod = sum % 11;

			if (this._getChecksum(mod) == checksum) {
				returnObj.status = true;

				return returnObj;
			} else {
				returnObj.status = false;
				returnObj.info = " 身份证号码输入错误";

				return returnObj;
			}
		} else {
			returnObj.status = false;
			returnObj.info = " 身份证号码格式错误";

			return returnObj;
		}
	},
	
	_splitId : function(_id) {
		var len = _id.length;
		var array = new Array();

		for ( var i = 0; i < len - 1; i++) {
			array.push(_id.charAt(i));
		}

		return array;
	},
	
	_getWeightingFactor : function(_index) {
		switch (_index) {
		case 1:
			return 7;
		case 2:
			return 9;
		case 3:
			return 10;
		case 4:
			return 5;
		case 5:
			return 8;
		case 6:
			return 4;
		case 7:
			return 2;
		case 8:
			return 1;
		case 9:
			return 6;
		case 10:
			return 3;
		case 11:
			return 7;
		case 12:
			return 9;
		case 13:
			return 10;
		case 14:
			return 5;
		case 15:
			return 8;
		case 16:
			return 4;
		case 17:
			return 2;
		default:
			return -1;
		}
	},
	_getChecksum : function(_mod) {
		switch (_mod) {
		case 0:
			return 1;
		case 1:
			return 0;
		case 2:
			return "X";
		case 3:
			return 9;
		case 4:
			return 8;
		case 5:
			return 7;
		case 6:
			return 6;
		case 7:
			return 5;
		case 8:
			return 4;
		case 9:
			return 3;
		case 10:
			return 2;
		default:
			return -1;
		}
	}
};