话不多说直接上代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>手写可拖曳 div</title>
<style>
.box {
width: 200px;
height: 200px;
border: 1px solid red;
position: relative;
}
</style>
</head>
<body>
<div id="box" class="box"></div>
<script>
var dragging = false
var position = null
box.addEventListener('mousedown', function (e) {
dragging = true
position = [e.clientX, e.clientY]
})
document.addEventListener('mousemove', function (e) { // 1. 这里需要监听document,不能只监听div,否则当拖动过快鼠标移动到div之外时会拖动不了
if (!dragging) return
const x = e.clientX
const y = e.clientY
const dataX = x - position[0]
const dataY = y - position[1]
const left = parseInt(box.style.left || 0)
const top = parseInt(box.style.top || 0)
box.style.left = left + dataX + 'px' // 2. 这里可以优化成transform,使用 transform 会比 top / left 性能更好,因为可以避免 reflow 和 repaint
box.style.top = top + dataY + 'px' // 这里同上
position = [x, y]
})
document.addEventListener('mouseup', function (e) {
dragging = false
})
</script>
</body>
</html>
注意:
- 注意监听范围,不能只监听 div
- 使用 transform 会比 top / left 性能更好,因为可以避免 reflow 和 repaint