getBoundingClientRect获取元素在页面上的位置

时间：2023-11-15 14:52:41

getBoundingClientRect用于获得页面中某个元素的左，上，右和下分别相对浏览器视窗的位置。

getBoundingClientRect是DOM元素到浏览器可视范围的距离（不包含文档卷起的部分）。

该函数返回一个Object对象，该对象有6个属性：top,lef,right,bottom,width,height；

这里的top、left和css中的理解很相似，width、height是元素自身的宽高，但是right，bottom和css中的理解有点不一样。right是指元素右边界距窗口最左边的距离，bottom是指元素下边界距窗口最上面的距离。

getBoundingClientRect最先是IE的私有属性，现在已经是一个W3C标准。所以不用担心浏览器兼容问题，不过还是有区别的：IE只返回top,lef,right,bottom四个值，width,height的值需要用right-left,bottom-top算出来。

var ele = document.getElementById("demo").getBoundingClientRect(),
     t = ele.top,
     b = ele.bottom,
     l = ele.left,
     r = ele.right,
     w = ele.width || r - l,
     h = ele.height || b - t;

写了个DEMO，如下：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

<title>getBoundingClientRect</title>

</head>

<body>

<script>

var $ = function (id) {

    return "string" == typeof id ? document.getElementById(id) : id;

};

var Class = {

    create: function() {

        return function() { this.initialize.apply(this, arguments); }

    }

}

var Bind = function(object, fun) {

    return function() {

        return fun.apply(object, arguments);

    }

}

var BindAsEventListener = function(object, fun) {

    return function(event) {

        return fun.call(object, (event || window.event));

    }

}

function addEventHandler(oTarget, sEventType, fnHandler) {

    if (oTarget.addEventListener) {

        oTarget.addEventListener(sEventType, fnHandler, false);

    } else if (oTarget.attachEvent) {

        oTarget.attachEvent("on" + sEventType, fnHandler);

    } else {

        oTarget["on" + sEventType] = fnHandler;

    }

};

function removeEventHandler(oTarget, sEventType, fnHandler) {

    if (oTarget.removeEventListener) {

        oTarget.removeEventListener(sEventType, fnHandler, false);

    } else if (oTarget.detachEvent) {

        oTarget.detachEvent("on" + sEventType, fnHandler);

    } else {

        oTarget["on" + sEventType] = null;

    }

};

var SimpleDrag = Class.create();

SimpleDrag.prototype = {

  initialize: function(drag) {

    this.Drag = $(drag);

    this.left = $("left");

    this.right = $("right");

    this.top = $("top");

    this.bottom = $("bottom");

    this.width = $("width");

    this.height = $("height");

    this._x = this._y = 0;

    this._fM = BindAsEventListener(this, this.Move);

    this._fS = Bind(this, this.Stop);

    this.Drag.style.position = "absolute";

    addEventHandler(this.Drag, "mousedown", BindAsEventListener(this, this.Start));

  },

  Start: function(oEvent) {

    this._x = oEvent.clientX - this.Drag.offsetLeft;

    this._y = oEvent.clientY - this.Drag.offsetTop;

    addEventHandler(document, "mousemove", this._fM);

    addEventHandler(document, "mouseup", this._fS);

  },

  Move: function(oEvent) {

      this.clsSelect();

    this.Drag.style.left = oEvent.clientX - this._x + "px";

    this.Drag.style.top = oEvent.clientY - this._y + "px";

    //获取元素位置代码

    this.left.innerHTML = this.Drag.getBoundingClientRect().left;

    this.right.innerHTML = this.Drag.getBoundingClientRect().right;

    this.top.innerHTML = this.Drag.getBoundingClientRect().top;

    this.bottom.innerHTML = this.Drag.getBoundingClientRect().bottom;

    this.width.innerHTML = this.Drag.getBoundingClientRect().width||this.Drag.getBoundingClientRect().right-this.Drag.getBoundingClientRect().left;

    this.height.innerHTML = this.Drag.getBoundingClientRect().height||this.Drag.getBoundingClientRect().bottom-this.Drag.getBoundingClientRect().top;

  },

  Stop: function() {

    removeEventHandler(document, "mousemove", this._fM);

    removeEventHandler(document, "mouseup", this._fS);

  },

  clsSelect:'getSelection' in window ? function () {

        window.getSelection().removeAllRanges();

    } : function () {

        try {

            document.selection.empty();

        } catch (e) {};

    }

};

</script>

<table width="300" border="1">

    <tr>

        <td colspan="2">信息</td>

    </tr>

    <tr>

        <td width="100">left:</td>

        <td id="left"></td>

    </tr>

    <tr>

        <td>top:</td>

        <td id="top"></td>

    </tr>

    <tr>

        <td>right:</td>

        <td id="right"></td>

    </tr>

    <tr>

        <td>bottom:</td>

        <td id="bottom"></td>

    </tr>

    <tr>

        <td>width:</td>

        <td id="width"></td>

    </tr>

    <tr>

        <td>height:</td>

        <td id="height"></td>

    </tr>

</table>

<div id="idDrag" style="background:blue; width:50px; height:50px;"></div>

<script>

new SimpleDrag("idDrag");

</script>

</body>

</html>

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