2020-05-04 用mouse事件写一个可拖曳的div

HTML

<div id="square"></div>

CSS

div{
  border: 1px solid red;
  position: absolute;
  top: 0;
  left: 0;
  width: 100px;
  height: 100px;
}

*{margin:0; padding: 0;}

JS

var isMousedown= false
var position = null

square.addEventListener('mousedown',function(e){
  isMousedown = true
  position = [e.clientX, e.clientY]
})


document.addEventListener('mousemove', function(e){
  if(isMousedown === false){return}
  const x = e.clientX
  const y = e.clientY
  const deltaX = x - position[0]
  const deltaY = y - position[1]
  const left = parseInt(square.style.left || 0)
  const top = parseInt(square.style.top || 0)
  square.style.left = left + deltaX + 'px'
  square.style.top = top + deltaY + 'px'
  position = [x, y]
})
document.addEventListener('mouseup', function(e){
  isMousedown = false
})