Method top

javascript/0155-min-stack.js:47–49

* @param {Array} * @return {number}

(stack = this.stack)

     * @return {number}
     */
    top(stack = this.stack) {
        return stack.length ? stack[stack.length - 1] /* Time O(1) */ : null;
    }

    /**
     * @return {number}