节流与防抖函数的实现

节流函数

/**
* @param {Function} fn 函数
*	@param {Number} time 时间
*/
function throttle(fn, time) {
	let previous = 0
  return function() {
  	const now = Date.now()
    const that = this
    const args = arguments
    if (now - previous > time) {
    	fn.apply(that, args)
      previous = now
    }
  }
}

防抖函数

/**
* @param {Function} fn 函数
*	@param {Number} time 延迟执行毫秒数
* @param {Boolean} immediate true - 立即执行 false - 延迟执行
*/
function debounce(fn, time = 1000, immediate = true) {
	let timer
  return function() {
  	const that = this
    const args = arguments
    if (timer) {
    	return clearTimeout(timer)
    }
    if (immediate) {
    	const callNow = !timer
      timer = setTimeout(() => {
      	timer = null
      }, time)
      if (callNow) {
      	fn.apply(that, args)
      }
    } else {
    	timer = setTimeout(() => {
      	fn.apply(that, args)
      }, time)
    }
  }
}