手写防抖（debounce）和节流（throttle）函数

function debounce(fn, delay, immediate = false) {
  let timer = null

  return function (...args) {
    if (timer) clearTimeout(timer)

    if (immediate && !timer) {
      fn.apply(this, args)
    }

    timer = setTimeout(() => {
      if (!immediate) fn.apply(this, args)
      timer = null
    }, delay)
  }
}

// 使用
input.addEventListener('input', debounce(search, 300))
window.addEventListener('resize', debounce(updateLayout, 200))

// 时间戳版（第一次立即执行，最后一次不执行）
function throttle(fn, interval) {
  let lastTime = 0
  return function (...args) {
    const now = Date.now()
    if (now - lastTime >= interval) {
      lastTime = now
      fn.apply(this, args)
    }
  }
}

// 定时器版（第一次不执行，最后一次会执行）
function throttle(fn, interval) {
  let timer = null
  return function (...args) {
    if (!timer) {
      timer = setTimeout(() => {
        fn.apply(this, args)
        timer = null
      }, interval)
    }
  }
}

// 组合版（第一次和最后一次都执行）
function throttle(fn, interval) {
  let lastTime = 0
  let timer = null
  return function (...args) {
    const now = Date.now()
    const remaining = interval - (now - lastTime)

    if (remaining <= 0) {
      if (timer) { clearTimeout(timer); timer = null }
      lastTime = now
      fn.apply(this, args)
    } else if (!timer) {
      timer = setTimeout(() => {
        lastTime = Date.now()
        timer = null
        fn.apply(this, args)
      }, remaining)
    }
  }
}