leetCode/2666.只允许一次函数调用.html

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    <title>2666. 只允许一次函数调用</title>
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    <script>
      // https://leetcode.cn/problems/allow-one-function-call/description/

      // 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。
      //
      // 提示：
      // 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 。
      //
      // 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

      /**
       * @param {Function} fn
       * @return {Function}
       */
      var once = function (fn) {
        return function (...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
       */

      // --- answer-1 ---

      // 搞个标志位
      var once = function (fn) {
        let called = false;
        return function (...args) {
          if (!called) {
            called = true;
            return fn.apply(this, args);
          }
        };
      };

      // --- answer-1 ---

      // --- answer-2 ---

      // --- answer-2 ---

      var fn = (a, b, c) => a + b + c,
        calls = [
          [1, 2, 3],
          [2, 3, 6]
        ];
      var result = [{ calls: 1, value: 6 }];
      // 解释：

      // var fn = (a,b,c) => (a * b * c), calls = [[5,7,4],[2,3,6],[4,6,8]];
      // var result = [{"calls":1,"value":140}];
      // 解释：

      // console.log('fn = ', fn);

      console.log('result = ', result);
      // console.log('once = ', once(fn));

      let fn = (a, b, c) => a + b + c;
      let onceFn = once(fn);

      console.log('1 = ', onceFn(1, 2, 3)); // 6
      console.log('2', onceFn(2, 3, 6)); // 6
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