实现 batchFn 函数，可以批量执行函数

let executeCount = 0;
const targetFn = async (nums) => {
  executeCount++;
  return nums.map((num) => 2 * num + 1);
};
 
const batcher = (fn) => {
  // todo batch logic
  return () => {};
};
 
const batchedFn = batcher(targetFn);
 
const main = async () => {
  const [result1, result2, result3] = await Promise.all([
    batchedFn([1, 2, 3]),
    batchedFn([4, 5]),
    batchedFn([6, 7]),
  ]);
 
  console.log(result1, result2, result3);
  console.log(executeCount); // 预期为 1
};
 
main();

const batcher = (fn) => {
  // todo batch logic
  let allArgs = [];
  // 能够实现 batch 的关键所在
  // 此处 fn(allArgs) 甚至可以实现为 fn([...new Set(allArgs)])，性能更好一些
  const wait = Promise.resolve().then(() => fn(allArgs));
 
  return async (args) => {
    allArgs = [...allArgs, ...args];
    const result = await wait;
 
    // allArgs 与 result 形成的一个 Map
    // 借助于 lodash 可以更可读化地写成 Object.fromEntries(_.zip(allArgs, result))
    const resultMap = result.reduce((acc, x, i) => {
      const v = allArgs[i];
      acc[v] = x;
      return acc;
    }, {});
    return args.map((a) => resultMap[a]);
  };
};