README.md

comments	difficulty	edit_url	tags
true	简单	https://github.com/doocs/leetcode/edit/main/solution/2600-2699/2666.Allow%20One%20Function%20Call/README.md	JavaScript

2666. 只允许一次函数调用

English Version

题目描述

给定一个函数 fn ，它返回一个新的函数，返回的函数与原始函数完全相同，只不过它确保 fn 最多被调用一次。

• 第一次调用返回的函数时，它应该返回与 fn 相同的结果。
• 第一次后的每次调用，它应该返回 undefined 。

 

示例 1：

输入：fn = (a,b,c) => (a + b + c), calls = [[1,2,3],[2,3,6]]
输出：[{"calls":1,"value":6}]
解释：
const onceFn = once(fn);
onceFn(1, 2, 3); // 6
onceFn(2, 3, 6); // undefined, fn 没有被调用

示例 2：

输入：fn = (a,b,c) => (a * b * c), calls = [[5,7,4],[2,3,6],[4,6,8]]
输出：[{"calls":1,"value":140}]
解释：
const onceFn = once(fn);
onceFn(5, 7, 4); // 140
onceFn(2, 3, 6); // undefined, fn 没有被调用
onceFn(4, 6, 8); // undefined, fn 没有被调用

 

提示：

• calls 是一个有效的 JSON 数组
• 1 <= calls.length <= 10
• 1 <= calls[i].length <= 100
• 2 <= JSON.stringify(calls).length <= 1000

解法

方法一

TypeScript

type JSONValue = null | boolean | number | string | JSONValue[] | { [key: string]: JSONValue };
type OnceFn = (...args: JSONValue[]) => JSONValue | undefined;

function once(fn: Function): OnceFn {
    let called = false;
    return function (...args) {
        if (!called) {
            called = true;
            return fn(...args);
        }
    };
}

/**
 * let fn = (a,b,c) => (a + b + c)
 * let onceFn = once(fn)
 *
 * onceFn(1,2,3); // 6
 * onceFn(2,3,6); // returns undefined without calling fn
 */

JavaScript

/**
 * @param {Function} fn
 * @return {Function}
 */
var once = function (fn) {
    let called = false;
    return function (...args) {
        if (!called) {
            called = true;
            return fn(...args);
        }
    };
};

/**
 * let fn = (a,b,c) => (a + b + c)
 * let onceFn = once(fn)
 *
 * onceFn(1,2,3); // 6
 * onceFn(2,3,6); // returns undefined without calling fn
 */