闭包在JavaScript中的数据隐藏与校验作用

function createAccount(initialBalance) {
  let balance = initialBalance; // 外部不可见、不可赋值
<p>return {
getBalance() { return balance; },
deposit(amount) {
if (amount > 0) balance += amount;
else throw new Error("Deposit must be positive");
},
withdraw(amount) {
if (amount > 0 && amount <= balance) {
balance -= amount;
} else {
throw new Error("Invalid withdrawal amount");
}
}
};
}</p><p>const account = createAccount(100);
account.deposit(50);       // ✅ 允许
console.log(account.getBalance()); // 150
account.balance = 0;        // ❌ 无效：balance 是私有变量，无此属性
</p>

function createIDCard(idNumber) {
  // 一次性校验 + 封装
  if (!/^\d{17}[\dXx]$/.test(idNumber)) {
    throw new Error("Invalid ID format");
  }
<p>const isValid = () => {
// 完整性校验逻辑（如校验码）可放在此处，与 idNumber 同一闭包
const weights = [7,9,10,5,8,4,2,1,6,3,7,9,10,5,8,4,2];
const checkCodes = ['1','0','X','9','8','7','6','5','4','3','2'];
const digits = idNumber.toUpperCase().split('').slice(0, -1).map(Number);
const sum = digits.reduce((s, d, i) => s + d * weights[i], 0);
return idNumber.slice(-1) === checkCodes[sum % 11];
};</p><p>return {
getID() { return idNumber; },
isValid: isValid // 校验能力随数据一同封闭
};
}
</p>

const privateData = new WeakMap();
<p>class BankTransaction {
constructor(amount, type) {
// 私有字段存于 WeakMap，仅本实例可访问
privateData.set(this, {
timestamp: Date.now(),
validated: false,
validate() {
if (amount <= 0) throw new Error("Amount must be positive");
if (!['deposit', 'withdraw'].includes(type)) 
throw new Error("Invalid transaction type");
this.validated = true;
}
});
}</p><p>execute() {
const data = privateData.get(this);
data.validate(); // 触发完整性检查
return <code>Executed ${this.constructor.name}</code>;
}
}
</p>