JavaScript-如何通过原生JS实现匀速动画

据我们所知，我们可以通过css3（transform translate即可）区实现这个动画，但是通常面试的时候，可能会被要求原生手敲；

使用到的知识点：定时器去实现setInterval去实现

js 复制代码

<button onclick="changeBox()">点击移动box</button>
    <div class="box"></div>
    <script>
        let box = document.querySelector('.box')
        let timerId 
        let timerId2
        function changeBox(){
            if(timerId2){clearTimeout(timerId2)}
            timerId2 = setTimeout(()=>{
                // if(timerId){clearInterval(timerId)}
                let original = box.offsetLeft;
                let current = 0
                timerId = setInterval(()=>{
                    current++
                    box.style.left = original + current + 'px'
                    // 比如移动到100px的时候就停止
                    console.log(current === 100,"查看防抖是否生效")
                    if(current === 100){
                        clearInterval(timerId)
                    }
                },10)
            },1000)
        }
    </script>

对于以上代码进行公共封装：元素原生实现匀速动画

js 复制代码

  /**
  * @target <Object> 传入的目标元素
  * @moveData <number> 每次点击移动数据
 * **/
function animate(target, moveData,callback) {
   if (target.timerId) {
       clearInterval(target.timerId)
   }
   let original = target.offsetLeft;
   let current = 0
       target.timerId = setInterval(() => {
         current++
         box.style.left = original + current + 'px'
           if (current === moveData) {
              clearInterval(target.timerId)
              if (callback instanceof Function) {
            	callback()
         	}
           }
         }, 10)
       }

缓动动画封装（匀速、加速、减速、返回加速、返回减速）

前面可以看到，我们使用current++是一种匀速的方式，匀速的快慢取决于我们+=后面的值，如果我们希望是缓动动画的形式去移动我们的元素，我们可以通过以下封装算法去实现

js 复制代码

 /** 清除定时器的时候需要注意的判断，非匀速是会有差别的
* if (current <0  || current == 0) {
     clearInterval(timerId4)
     box.style.left =original + 'px'
	}else{
		box.style.left =original + current + 'px'
     }
 **/function speed (type, moveData) {
  switch (type) {
    case 'uniformSpeed': // 匀速
      function uniformSpeed () {
        let current = 0
        return current++
      }
      return speed++
      break
    case 'moderate': // 减速
      function moderate (moveData) {
        let current = 0
        let distance = moveData - current
        return (current += distance
          ? Math.ceil(distance / 10)
          : Math.floor(distance / 10))
      }
      break
    case 'accelerate': // 加速
      function accelerate (moveData) {
        let current = 0
        let distance = 10 + current
        return current < 500
          ? (current += distance
              ? Math.ceil(distance / 10)
              : Math.floor(distance / 10))
          : 500
      }
      break
    case 'comeBack-accelerate': // 往回加速
      function comeBack (moveData) {
        let current = moveData
        let distance = 10 + current
        current -=
          distance > 0 ? Math.ceil(distance / 10) : Math.floor(distance / 10)
      }
      break
    case 'comeBack-moderate': // 往回减速速
      function comeBack (moveData) {
        let current = 0
        let distance = moveData - current
        return (current -= distance
          ? Math.ceil(distance / 10)
          : Math.floor(distance / 10))
      }
      break
  }
}