如何在香草javascript中实现lodash _.throttle？

Question

我正在尝试实现Lodash的_.throttle。我知道需要返回什么（总变量），但无法弄清楚如何将所有内容放在一起。有一些摩卡测试可以帮助我理解这一点，我将在下面发布。

我已经阅读了有关该主题的几篇博客文章，并尝试将setTimeout与一个布尔值结合使用，该布尔值确定是否需要运行setTimeout，但是我的测试仍然失败。

/*
Throttle
Creates and returns a new, throttled version of the passed function, that, when
invoked repeatedly, will only actually call the original function at most once
per every wait milliseconds. Useful for rate-limiting events that occur faster
than you can keep up with.
Example:
let total = 0;
const count = () => ++total;
const throttleCount = throttle(count, 200);
throttleCount()
=> 1
throttleCount()
=> 1
// Wait 200ms and then:
throttleCount()
=> 2
throttleCount()
=> 2
*/

// Your code here!
let total = 0;

const count = () => {
  return ++total
}

function throttle(callback, delay) {
  let wait = false 
  return function() {
    if (!wait) {
      wait = true
      callback()
      return total
    } else {
      setTimeout(function() {
        wait = false
      }, delay)
      return total
    }
  }
}

const throttleCount = throttle(count, 200)
throttleCount()
throttleCount()
throttleCount()
throttleCount()
throttleCount()
throttleCount()

const assert = require('assert');

describe('Throttle', () => {
  it('returns a function', () => {
    const exampleThrottle = throttle(() => {})
    assert.equal(typeof exampleThrottle, 'function');
  });
  it('effectively throttles', (done) => {
    let total = 0;
    const count = () => ++total;
    const throttleCount = throttle(count, 200);

    assert.equal(throttleCount(), 1);
    assert.equal(throttleCount(), 1);

    // Wait 200ms and try again
    new Promise(resolve => setTimeout(resolve, 200)).then(() => {
      assert.equal(throttleCount(), 2);
      assert.equal(throttleCount(), 2);
      done()
    })
  });
});

我无法返回setTimeout，因为它是未定义的。我还继续使用当前代码返回1。