Richard Tyson

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getBoundingClientRect获取元素在页面上的位置

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>

 

posted on 2014-10-18 00:46  tyson  阅读(536)  评论(0)  编辑  收藏  举报