# 拖拽
window.onload = function() {
// drag处于绝对定位状态
let drag = document.getElementById("box");
drag.onmousedown = function(e) {
var e = e || window.event;
// 鼠标与拖拽元素边界的距离 = 鼠标与可视区边界的距离 - 拖拽元素与边界的距离
let diffX = e.clientX - drag.offsetLeft;
let diffY = e.clientY - drag.offsetTop;
drag.onmousemove = function(e) {
// 拖拽元素移动的距离 = 鼠标与可视区边界的距离 - 鼠标与拖拽元素边界的距离
let left = e.clientX - diffX;
let top = e.clientY - diffY;
// 避免拖拽出可视区
if (left < 0) {
left = 0;
} else if (left > window.innerWidth - drag.offsetWidth) {
left = window.innerWidth - drag.offsetWidth;
}
if (top < 0) {
top = 0;
} else if (top > window.innerHeight - drag.offsetHeight) {
top = window.innerHeight - drag.offsetHeight;
}
drag.style.left = left + "px";
drag.style.top = top + "px";
};
drag.onmouseup = function(e) {
this.onmousemove = null;
this.onmouseup = null;
};
};
};
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← instanceof setTimeOut →