How do I retrieve an HTML element's actual wid

2018-12-31 06:50发布

站内问答 / JavaScript
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Suppose that I have a <div> that I wish to center in the browser's display (viewport). To do so, I need to calculate the width and height of the <div> element.

What should I use? Please include information on browser compatibility.

12条回答
不流泪的眼
2楼-- · 2018-12-31 07:28

Here is the code for WKWebView what determines a height of specific Dom element (doesn't work properly for whole page)

let html = "<body><span id=\"spanEl\" style=\"font-family: '\(taskFont.fontName)'; font-size: \(taskFont.pointSize - 4.0)pt; color: rgb(\(red), \(blue), \(green))\">\(textValue)</span></body>"
webView.navigationDelegate = self
webView.loadHTMLString(taskHTML, baseURL: nil)

func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
    webView.evaluateJavaScript("document.getElementById(\"spanEl\").getBoundingClientRect().height;") { [weak self] (response, error) in
        if let nValue = response as? NSNumber {

        }
    }
}
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栀子花@的思念
3楼-- · 2018-12-31 07:33

According to MDN: Determining the dimensions of elements

offsetWidth and offsetHeight return the "total amount of space an element occupies, including the width of the visible content, scrollbars (if any), padding, and border"

clientWidth and clientHeight return "how much space the actual displayed content takes up, including padding but not including the border, margins, or scrollbars"

scrollWidth and scrollHeight return the "actual size of the content, regardless of how much of it is currently visible"

So it depends on whether the measured content is expected to be out of the current viewable area.

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姐姐魅力值爆表
4楼-- · 2018-12-31 07:34

element.offsetWidth and element.offsetHeight should do, as suggested in previous post.

However, if you just want to center the content, there is a better way of doing so. Assuming you use xhtml strict DOCTYPE. set the margin:0,auto property and required width in px to the body tag. The content gets center aligned to the page.

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弹指情弦暗扣
5楼-- · 2018-12-31 07:36

Take a look at Element.getBoundingClientRect().

This method will return an object containing the width, height, and some other useful values:

{
    width: 960,
    height: 71,
    top: 603,
    bottom: 674,
    left: 360,
    right: 1320
}

For Example:

var element = document.getElementById('foo');
var positionInfo = element.getBoundingClientRect();
var height = positionInfo.height;
var width = positionInfo.width;

I believe this does not have the issues that .offsetWidth and .offsetHeight do where they sometimes return 0 (as discussed in the comments here)

Another difference is getBoundingClientRect() may return fractional pixels, where .offsetWidth and .offsetHeight will round to the nearest integer.

IE8 Note: getBoundingClientRect does not return height and width on IE8 and below.*

If you must support IE8, use .offsetWidth and .offsetHeight:

var height = element.offsetHeight;
var width = element.offsetWidth;

Its worth noting that the Object returned by this method is not really a normal object. Its properties are not enumerable (so, for example, Object.keys doesn't work out-of-the-box.)

More info on this here: How best to convert a ClientRect / DomRect into a plain Object

Reference:

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何处买醉
6楼-- · 2018-12-31 07:41

You should use the .offsetWidth and .offsetHeight properties. Note they belong to the element, not .style.

var width = document.getElementById('foo').offsetWidth;

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时光乱了年华
7楼-- · 2018-12-31 07:41

You only need to calculate it for IE7 and older (and only if your content doesn't have fixed size). I suggest using HTML conditional comments to limit hack to old IEs that don't support CSS2. For all other browsers use this:

<style type="text/css">
    html,body {display:table; height:100%;width:100%;margin:0;padding:0;}
    body {display:table-cell; vertical-align:middle;}
    div {display:table; margin:0 auto; background:red;}
</style>
<body><div>test<br>test</div></body>

This is the perfect solution. It centers <div> of any size, and shrink-wraps it to size of its content.

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