代码块

继承

function create(o) {
  function F() {}
  F.prototype = o
  return new F()
}

function inherit(child, parent) {
  let prototype = create(parent.prototype)
  prototype.constructor = child
  child.prototype = prototype
}

防抖

N秒后只会执行一次，如果 N 秒内事件再次触发，则会重新计时，例：input输入参考

function debounce(func, wait, immediate) {
  let timer, result
  let debounced = function() {
    let args = arguments
    let context = this
    
    if (timer) {
      clearTimeout(timer)
    }

    if (immediate) {
      let callNow = !timer
      timer = setTimeout(() => {
        timer = null
      }, wait);
      if (callNow) {
        func.apply(context, args)
      }
    } else {
      timer = setTimeout(function() {
        func.apply(context, args)
      }, wait);
    }
  }
  debounced.cancel = function() {
    clearTimeout(timer)
    timer = null
  }
  return debounced
}

let count = 1
let container = document.getElementById('container')

function getUserAction(e) {
  container.innerHTML = count++
}

let setUseAction = debounce(getUserAction, 1000, true)
container.onmousemove = setUseAction
document.getElementById("button").addEventListener('click', function(){
    setUseAction.cancel();
})

节流

N秒内只执行一次，例：滑动页面

function throttle(func, wait) {
  let timer
  
  return function() {
    let arg = arguments
    let context = this
    if (timer) {
      return
    }
    timer = setTimeout(function() {
      func.apply(context, arg)
      timer = null
    }, wait)
  }
}

function throttle2(func, wait) {
  let previous = 0
  return function() {
    let arg = arguments
    let context = this
    let now = +new Date()
    if (now - previous > wait) {
      previous = now
      func.apply(context, arg)
    }
  }
}

const container = document.getElementById('container')
container.onmousemove = throttle2(function() {
  console.log(11111)
}, 3000)

柯里化

只传递给函数一部分参数来调用它，让它返回一个函数去处理剩下的参数

function currying(fn, ...args) {
  if (args.length >= fn.length) {
    return fn(...args)
  }

  return function(...args2) {
    return currying(fn, ...args, ...args2)
  }
}

function add(x, y) {
  return x + y
}

const increment = currying(add, 1)
const a = increment(2)

console.log(a)

lazyLoad

const imgs = document.getElementsByTagName('img')
const viewHeight = window.innerHeight || document.documentElement.clientHeight
let num = 0

function lazyload() {
  for (let i = num; i< imgs.length; i++) {
    let distance = viewHeight - imgs[i].getBoundingClientRect().top
    if (distance >= 0) {
      imgs[i].src = imgs[i].getAttribute('data-src')
      num = i + 1
    }
  }
}

window.addEventListener('scroll', lazyload, false)