使用JavaScript实现一个拖拽缩放效果

<style>
  .box{
    margin: 50px;
    width: 500px;
    height: 300px;
    border: 1px solid black;
    position: relative;
  }
  .drag{
    height: 100px;
    width: 100px;
    background-color: #cbd;
  }
</style>

<div class="box">
  <div class="drag"></div>
</div>

<script>
  let dragEl = document.querySelector(".drag")
  let container = document.querySelector(".box")
  let width, height, maxWidth, maxHeight, tx, ty, startX, startY
  // 初始化
  function init() {
    // 为目标元素设置初始的偏移，避免在第一次获取偏移时为空的问题
    dragEl.style.transfORM = "translate(0px,0px)"
    // 获取父元素宽高
    maxWidth = container.clientWidth
    maxHeight = container.clientHeight
  }
  function getInfo(e) {
      // 获取元素当前的宽高
      width = dragEl.clientWidth
      height = dragEl.clientHeight
      // 获取元素当前的偏移量
      let translateStr = dragEl.style.transform
      const reg = /\d+/g
      let translateArr = translateStr.match(reg)
      tx = Number(translateArr[0])
      ty = Number(translateArr[1])
      // 记录鼠标的起始位置
      startX = e.clientX
      startY = e.clientY
    }
  function  drag() {
    dragEl.addEventListener("mousedown", (e) => {
      getInfo(e)
      document.onmousemove = (e) => {
        let distanceX = tx + e.clientX - startX
        let distanceY = ty + e.clientY - startY
        dragEl.style.transform = `translate(${distanceX}px, ${distanceY}px)`
      }
      document.onmouseup = () => {
        document.onmousemove = null
      }
    })
  }
  init()
  drag()
</script>

let distanceX = Math.max(0, Math.min(tx + e.clientX - startX, maxWidth - width))
let distanceY = Math.max(0, Math.min(ty + e.clientY - startY, maxHeight - height))

<style>
  .box{
    margin: 50px;
    width: 500px;
    height: 300px;
    border: 1px solid black;
    position: relative;
  }
  .drag{
    height: 100px;
    width: 100px;
    background-color: #cbd;
  }
  .left{
    width: 10px;
    height: calc(100% - 14px);
    margin: 7px 0px;
    position: absolute;
    background-color: #000;
    cursor: col-resize;
    top: 0;
    left: -5px;
  }
</style>
<script>
function addLeft() {
  left = document.createElement("div")
  left.className = "left"
  dragEl.append(left)
}
init()
drag()
addLeft()
</script>

function leftZoom() {
  left.addEventListener("mousedown", (e) => {
    e.stopPropagation()
    getInfo(e)
    document.onmousemove = (e) => {
      // 注意这里是➖
      newWidth = width - (e.clientX - startX)
      let distanceX = tx + (e.clientX - startX)
      dragEl.style.width = `${newWidth}px`
      dragEl.style.transform = `translate(${distanceX}px, ${ty}px)`
    }
    document.onmouseup = () => {
      document.onmousemove = null
    }
  })
}
init()
drag()
addLeft()
leftZoom()

let minWidth = 30
newWidth = Math.max(minWidth, width - (e.clientX - startX))

// 最大偏移为已经偏移的距离 + 目标元素的宽度 - 最小宽度
let distanceX = Math.min(tx + width - minWidth, tx + (e.clientX - startX))

// 最大宽度为元素当前偏移量 + 最初的宽度，最小宽度为minWidth
newWidth = Math.min(tx + width, Math.max(minWidth, width - (e.clientX - startX)))
// 最大偏移为已经偏移的距离 + 目标元素的宽度 - 最小宽度,最小偏移为0
let distanceX = Math.max(0,Math.min(tx + width - minWidth, tx + (e.clientX - startX)))