栈

class Stack {
    constructor() {
        this.list = [];
    }
    push(value) {
        this.list.push(value);
    }
    pop() {
        return this.list.pop();
    }
    peek() {
        return this.list[this.list.length - 1]
    }
    size() {
        return this.list.length;
    }
    isEmpty() {
        return this.list.length === 0;
    }
    clear() {
        this.list = [];
    }
    toString() {
        return this.list.join(",")
    }
}

// 测试代码
const stack = new Stack();
stack.push(1)
stack.push(3)
stack.push(5)
stack.pop();
stack.push(7)
console.log(stack.peek())
console.log(stack.size())
console.log(stack.isEmpty())
console.log("toString =",stack.toString())
stack.clear();
console.log(stack.isEmpty())
console.log("toString =",stack.toString())