你应该使用. offsetwidth和. offsetheight属性。 注意它们属于元素，而不是.style。

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

. getboundingclientrect()函数的作用是:在执行CSS转换后，以浮点数的形式返回元素的尺寸和位置。

> console.log(document.getElementById('foo').getBoundingClientRect())
DOMRect {
    bottom: 177,
    height: 54.7,
    left: 278.5,​
    right: 909.5,
    top: 122.3,
    width: 631,
    x: 278.5,
    y: 122.3,
}

我为此创建了一个具有高度灵活性的效用函数:

export type Size = {width: number, height: number};
export enum GetSize_Method {
    /** Includes: content, padding. Excludes: border, margin, scroll-bar (if it has one), "position:absolute" descendants. */
    ClientSize = "ClientSize",
    /** Includes: content, padding, border, margin, scroll-bar (if it has one). Excludes: "position:absolute" descendants. */
    OffsetSize = "OffsetSize",
    /** Includes: content, padding, border, margin, scroll-bar (if it has one), "position:absolute" descendants. Excludes: none. */
    ScrollSize = "ScrollSize",
    /** Same as ScrollSize, except that it's calculated after the element's css transforms are applied. */
    BoundingClientRect = "BoundingClientRect",
    /** Lets you specify the exact list of components you want to include in the size calculation. */
    Custom = "Custom",
}
export type SizeComp = "content" | "padding" | "border" | "margin" | "scrollBar" | "posAbsDescendants";

export function GetSize(el: HTMLElement, method = GetSize_Method.ClientSize, custom_sizeComps?: SizeComp[]) {
    let size: Size;
    if (method == GetSize_Method.ClientSize) {
        size = {width: el.clientWidth, height: el.clientHeight};
    } else if (method == GetSize_Method.OffsetSize) {
        size = {width: el.offsetWidth, height: el.offsetHeight};
    } else if (method == GetSize_Method.ScrollSize) {
        size = {width: el.scrollWidth, height: el.scrollHeight};
    } else if (method == GetSize_Method.BoundingClientRect) {
        const rect = el.getBoundingClientRect();
        size = {width: rect.width, height: rect.height};
    } else if (method == GetSize_Method.Custom) {
        const style = window.getComputedStyle(el, null);
        const styleProp = (name: string)=>parseFloat(style.getPropertyValue(name));

        const padding = {w: styleProp("padding-left") + styleProp("padding-right"), h: styleProp("padding-top") + styleProp("padding-bottom")};
        const base = {w: el.clientWidth - padding.w, h: el.clientHeight - padding.h};
        const border = {w: styleProp("border-left") + styleProp("border-right"), h: styleProp("border-top") + styleProp("border-bottom")};
        const margin = {w: styleProp("margin-left") + styleProp("margin-right"), h: styleProp("margin-top") + styleProp("margin-bottom")};
        const scrollBar = {w: (el.offsetWidth - el.clientWidth) - border.w - margin.w, h: (el.offsetHeight - el.clientHeight) - border.h - margin.h};
        const posAbsDescendants = {w: el.scrollWidth - el.offsetWidth, h: el.scrollHeight - el.offsetHeight};

        const sc = (name: SizeComp, valIfEnabled: number)=>custom_sizeComps.includes(name) ? valIfEnabled : 0;
        size = {
            width: sc("content", base.w) + sc("padding", padding.w) + sc("border", border.w)
                    + sc("margin", margin.w) + sc("scrollBar", scrollBar.w) + sc("posAbsDescendants", posAbsDescendants.w),
            height: sc("content", base.h) + sc("padding", padding.h) + sc("border", border.h)
                    + sc("margin", margin.h) + sc("scrollBar", scrollBar.h) + sc("posAbsDescendants", posAbsDescendants.h),
        };
    }
    return size;
}

用法:

const el = document.querySelector(".my-element");
console.log("Size:", GetSize(el, "ClientSize"));
console.log("Size:", GetSize(el, "Custom", ["content", "padding", "border"]));

Flex

如果你想在<div>中显示屏幕中心的某种弹出消息，那么你不需要读取<div>的大小，但你可以使用flex

.box { 宽度:50 px; 高度:20 px; 背景:红色; ｝ .container { 显示:flex; justify-content:中心; 对齐项目:中心; 身高:100 vh; 宽度:100大众; 位置:固定;/*如果div下没有内容，则删除它(并且记住将正文边距设置为0)*/ ｝ < div class = "容器" > <div class="box">我的div</div> < / div >

如果offsetWidth返回0，你可以获取元素的样式宽度属性并搜索一个数字。100px -> 100

/ \ d * / .exec (MyElement.style.width)

下面是WKWebView的代码，它决定了特定Dom元素的高度(不适用于整个页面)

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 {

        }
    }
}

看一下Element.getBoundingClientRect()。

这个方法将返回一个包含宽度、高度和其他一些有用值的对象:

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

例如:

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

我相信这没有.offsetWidth和.offsetHeight的问题，它们有时返回0(如在这里的评论中讨论的那样)

另一个区别是getBoundingClientRect()可能返回分数像素，其中. offsetwidth和. offsetheight将四舍五入到最近的整数。

注意:getBoundingClientRect在IE8及以下不返回高度和宽度

如果你必须支持IE8，使用.offsetWidth和.offsetHeight:

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

值得注意的是，该方法返回的对象并不是真正的普通对象。它的属性是不可枚举的(例如，Object。钥匙不能开箱即用。)

更多信息请点击这里: 如何最好地将一个ClientRect / DomRect转换为一个普通对象

参考:

.offsetHeight: https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/offsetHeight .offsetWidth: https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/offsetWidth .getBoundingClientRect (): https://developer.mozilla.org/en-US/docs/Web/API/Element/getBoundingClientRect