vue 元素拖拽

效果演示：

前置知识理解图示：

代码1：

<template>
  <div class='container'>
    <div id="box1"></div>
  </div>
</template>

<script>
export default {
  data () {
    return {

    }
  },
  mounted () {
    this.moveEle()
  },
  methods: {
    moveEle () {
      const box1 = document.getElementById('box1')
      box1.onmousedown = (e) => {
        // 计算鼠标到元素X，Y距离
        const X = e.clientX - box1.offsetLeft
        const Y = e.clientY - box1.offsetTop
        const maxWidth = document.body.clientWidth - box1.offsetWidth
        const maxHeight = document.documentElement.clientHeight - box1.offsetHeight
        document.onmousemove = (event) => {
          event = event || window.event
          // 设置偏移量
          let left = event.clientX - X
          let top = event.clientY - Y
          if (left < 0) {
            left = 0
          } else if (left > maxWidth) {
            left = maxWidth
          }
          if (top < 0) {
            top = 0
          } else if (top > maxHeight) {
            top = maxHeight
          }
          // 修改box1的位置
          box1.style.left = left + 'px'
          box1.style.top = top + 'px'
        }
        document.onmouseup = () => {
          // 取消document的onmousemove和onmouseup事件 ！！！
          document.onmousemove = null
          document.onmouseup = null
        }
      }
    }

  }
}
</script>

<style scoped lang='scss'>
    #box1{
        width: 100px;
        height: 100px;
        left:10px;
        top:10px;
        background-color: red;
        position: absolute;
    }
</style>

代码2：

<template>
  <div class='container'>
    <div id="box1" @mousedown="moveEle"></div>
  </div>
</template>

<script>
export default {
  data () {
    return {

    }
  },
  methods: {
    moveEle (e) {
      const box1 = document.getElementById('box1')
      // 计算鼠标到元素X，Y距离
      const X = e.clientX - box1.offsetLeft
      const Y = e.clientY - box1.offsetTop
      const maxWidth = document.body.clientWidth - box1.offsetWidth
      const maxHeight = document.documentElement.clientHeight - box1.offsetHeight
      document.onmousemove = (event) => {
        event = event || window.event
        // 设置偏移量
        let left = event.clientX - X
        let top = event.clientY - Y
        // 控制在视图之内
        if (left < 0) {
          left = 0
        } else if (left > maxWidth) {
          left = maxWidth
        }
        if (top < 0) {
          top = 0
        } else if (top > maxHeight) {
          top = maxHeight
        }
        // 修改box1的位置
        box1.style.left = left + 'px'
        box1.style.top = top + 'px'
      }
      document.onmouseup = () => {
        // 取消document的onmousemove和onmouseup事件 ！！！
        document.onmousemove = null
        document.onmouseup = null
      }
    }

  }
}
</script>

<style scoped lang='scss'>
    #box1{
        width: 100px;
        height: 100px;
        left:10px;
        top:10px;
        background-color: red;
        position: absolute;
    }
</style>