原生js实现元素的拖拽和拉伸，需要清楚一下几个要素：
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网页可见区域宽： document.body.clientWidth 网页可见区域高： document.body.clientHeight 网页可见区域宽： document.body.offsetWidth (包括边线的宽) 网页可见区域高： document.body.offsetHeight (包括边线的高) 网页正文全文宽： document.body.scrollWidth 网页正文全文高： document.body.scrollHeight 网页被卷去的高： document.body.scrollTop 网页被卷去的左： document.body.scrollLeft
对应的dom元素的宽高有以下几个常用的： 元素的实际高度：document.getElementById("div").offsetHeight 元素的实际宽度：document.getElementById("div").offsetWidth 元素的实际距离左边界的距离：document.getElementById("div").offsetLeft 元素的实际距离上边界的距离：document.getElementById("div").offsetTop |
需要用到的几个鼠标事件：
mousedown——onmousemove ——onmouseup 分别是鼠标点击目标事件、鼠标在页面移动事件、鼠标离开目标事件
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>js实现拖拽和拉伸</title>
</head>
<body>
<div id="test" style="position:absolute;left:0;top:210PX;width:400px;height:400px; border:1px solid #adadad;"></div>
<div class="test" style="position:absolute;left:0px;top:0px;width:200px;height:200px; border:1px solid #adadad;"></div>
<div class="test" style="position:absolute;left:210px;top:0px;width:200px;height:200px; border:1px solid #adadad;"></div>
<div class="test" style="position:absolute;left:420px;top:0px;width:200px;height:200px; border:1px solid #adadad;"></div>
<script>
let arr=document.getElementsByClassName(\'test\')
for(var i=0;i<arr.length;i++){
let test=arr[i]
test.addEventListener(\'mousedown\',e=>{
var mouseDownX = e.clientX;
var mouseDownY = e.clientY;
var clickBoxLeft = test.offsetLeft;
var clickBoxTop = test.offsetTop;
var clickBoxWeight = test.offsetWidth;
var clickBoxHeight = test.offsetHeight;
var direction = 0;
if (mouseDownX < clickBoxLeft + 30) {
direction = \'left\';
} else if (mouseDownX > clickBoxLeft + clickBoxWeight - 30) {
direction = \'right\';
}
if (mouseDownY < clickBoxTop + 30) {
direction = \'top\';
} else if (direction < clickBoxTop + clickBoxHeight - 30) {
direction = \'bottom\';
}
if ((clickBoxLeft + clickBoxWeight - 30) < mouseDownX && mouseDownX < (clickBoxLeft + clickBoxWeight) && (clickBoxTop + clickBoxHeight - 30) < mouseDownY && mouseDownY < (clickBoxTop + clickBoxHeight)) {
direction = \'rightBottomCorner\';
} else if ((clickBoxLeft + 30) < mouseDownX && mouseDownX < (clickBoxLeft + clickBoxWeight - 30) && (clickBoxTop + 30) < mouseDownY && mouseDownY < (clickBoxTop + clickBoxHeight - 30)) { //如果是在中间位置，则实现拖动功能
direction = "drag";
}
document.onmousemove = function (e) {
var xx = e.clientX;
var yy = e.clientY;
if (direction === \'left\') {
test.style.width = clickBoxWeight + mouseDownX - xx + \'px\'
test.style.left = xx + \'px\';
} else if (direction === \'right\') {
test.style.width = clickBoxWeight + xx - mouseDownX + \'px\'
}
if (direction === \'top\') {
test.style.height = clickBoxHeight + mouseDownY - yy + \'px\';
test.style.top = yy + \'px\';
} else if (direction === \'bottom\') {
test.style.height = clickBoxHeight + yy - mouseDownY + \'px\';
}
if (direction === \'rightBottomCorner\') {
test.style.width = clickBoxWeight + xx - mouseDownX + \'px\'
test.style.left = clickBoxLeft + \'px\';
test.style.height = clickBoxHeight + yy - mouseDownY + \'px\';
test.style.top = clickBoxTop + \'px\';
} else if (direction === "drag") {
test.style.left = xx - mouseDownX + clickBoxLeft + \'px\';
test.style.top = yy - mouseDownY + clickBoxTop + \'px\';
}
//return false; //这里为了避免抖动
};
document.onmouseup = function () {
document.onmousemove = null;
document.onmouseup = null;
};
if (e.preventDefault) {
e.preventDefault();
}
})
}
var clickBox = document.getElementById(\'test\');
/**
*desc:当在当前元素上按下鼠标时，就触发拖动和拉伸操作
*/
clickBox.onmousedown =(e)=> {
console.log(clickBox)
var mouseDownX = e.clientX;
var mouseDownY = e.clientY;
var clickBoxLeft = clickBox.offsetLeft;
var clickBoxTop = clickBox.offsetTop;
var clickBoxWeight = clickBox.offsetWidth;
var clickBoxHeight = clickBox.offsetHeight;
var direction = 0;
if (mouseDownX < clickBoxLeft + 30) {
direction = \'left\';
} else if (mouseDownX > clickBoxLeft + clickBoxWeight - 30) {
direction = \'right\';
}
if (mouseDownY < clickBoxTop + 30) {
direction = \'top\';
} else if (direction < clickBoxTop + clickBoxHeight - 30) {
direction = \'bottom\';
}
if ((clickBoxLeft + clickBoxWeight - 30) < mouseDownX && mouseDownX < (clickBoxLeft + clickBoxWeight) && (clickBoxTop + clickBoxHeight - 30) < mouseDownY && mouseDownY < (clickBoxTop + clickBoxHeight)) {
direction = \'rightBottomCorner\';
} else if ((clickBoxLeft + 30) < mouseDownX && mouseDownX < (clickBoxLeft + clickBoxWeight - 30) && (clickBoxTop + 30) < mouseDownY && mouseDownY < (clickBoxTop + clickBoxHeight - 30)) { //如果是在中间位置，则实现拖动功能
direction = "drag";
}
/**
*desc:当鼠标开始华东的时候，根据鼠标的移动方向去调整他的X，Y坐标和长宽
*/
document.onmousemove = function (e) {
e = e || event; //是要是使用原生js给我们提供的e回调参数，这存储了很多有用的信息
var xx = e.clientX;
var yy = e.clientY;
if (direction === \'left\') {
clickBox.style.width = clickBoxWeight + mouseDownX - xx + \'px\'
clickBox.style.left = xx + \'px\';
} else if (direction === \'right\') {
clickBox.style.width = clickBoxWeight + xx - mouseDownX + \'px\'
}
if (direction === \'top\') {
clickBox.style.height = clickBoxHeight + mouseDownY - yy + \'px\';
clickBox.style.top = yy + \'px\';
} else if (direction === \'bottom\') {
clickBox.style.height = clickBoxHeight + yy - mouseDownY + \'px\';
}
if (direction === \'rightBottomCorner\') {
clickBox.style.width = clickBoxWeight + xx - mouseDownX + \'px\'
clickBox.style.left = clickBoxLeft + \'px\';
clickBox.style.height = clickBoxHeight + yy - mouseDownY + \'px\';
clickBox.style.top = clickBoxTop + \'px\';
} else if (direction === "drag") {
clickBox.style.left = xx - mouseDownX + clickBoxLeft + \'px\';
clickBox.style.top = yy - mouseDownY + clickBoxTop + \'px\';
}
//return false; //这里为了避免抖动
};
document.onmouseup = function () {
document.onmousemove = null;
document.onmouseup = null;
};
if (e.preventDefault) {
e.preventDefault();
}
};
// /**
// *desc:在拉伸的过程中，实现居中状态长存,有时间将其做成一个插件公布出来，供大家使用
// */
</script>
</body>
</html>
以上是参考https://blog.csdn.net/m0_37631322/article/details/89973554 的对于单独元素和多个元素的拖拽事件