krahets/hello-algo · error · Error

栈为空

Error message

栈为空

What it means

Thrown by pop() on an array-backed stack (ArrayStack) when the stack is empty (internal #stack.length === 0). pop() calls the native Array.pop after the guard; without the check, Array.pop would return undefined and the caller could mistake that for a value. This guard makes underflow explicit.

Source

Thrown at codes/javascript/chapter_stack_and_queue/array_stack.js:31

    /* 获取栈的长度 */
    get size() {
        return this.#stack.length;
    }

    /* 判断栈是否为空 */
    isEmpty() {
        return this.#stack.length === 0;
    }

    /* 入栈 */
    push(num) {
        this.#stack.push(num);
    }

    /* 出栈 */
    pop() {
        if (this.isEmpty()) throw new Error('栈为空');
        return this.#stack.pop();
    }

    /* 访问栈顶元素 */
    top() {
        if (this.isEmpty()) throw new Error('栈为空');
        return this.#stack[this.#stack.length - 1];
    }

    /* 返回 Array */
    toArray() {
        return this.#stack;
    }
}

/* Driver Code */
/* 初始化栈 */
const stack = new ArrayStack();

View on GitHub (pinned to 69932aed18)

Solutions

1. Check stack.isEmpty() before pop(): if (!stack.isEmpty()) stack.pop();.
2. Use a counted pop tied to a recorded push count.
3. In DFS, only pop a frame you pushed; assert the stack is non-empty before processing.
4. Prefer returning a sentinel (e.g. undefined or null) via a wrapper instead of relying on the throw for control flow.

Example fix

// before
const top = stack.pop(); // throws if empty
// after
const top = stack.isEmpty() ? null : stack.pop();

function safePop(stack) {
  return stack.isEmpty() ? null : stack.pop();
}

function stackNotEmpty(stack) {
  return !stack.isEmpty();
}

try {
  const x = stack.pop();
} catch (e) {
  if (e instanceof Error && e.message === '栈为空') { /* underflow */ } else throw e;
}

When it happens

Trigger: Calling pop() on a freshly constructed stack; popping more than was pushed; mismatched push/pop in a balanced-parentheses or DFS routine.

Common situations: Expression evaluation (too many operators); backtracking/DFS unwind past the start; reversing with push-all then pop-too-many.

Related errors

• スタックが空
• 栈为空
• Stack is empty
• Stack is empty
• スタックが空

AI-assisted analysis of krahets/hello-algo@69932aed18 (2026-08-13). Data as JSON: /api/errors/74680344fcd8c1cd. Report an issue: GitHub.