你也可以使用createRange，这比文本克隆技术更准确:

function getNodeTextWidth(nodeWithText) {
    var textNode = $(nodeWithText).contents().filter(function () {
        return this.nodeType == Node.TEXT_NODE;
    })[0];
    var range = document.createRange();
    range.selectNode(textNode);
    return range.getBoundingClientRect().width;
}

更好的方法是在显示元素之前检测文本是否合适。你可以使用这个函数它不需要元素在屏幕上。

function textWidth(text, fontProp) {
    var tag = document.createElement("div");
    tag.style.position = "absolute";
    tag.style.left = "-999em";
    tag.style.whiteSpace = "nowrap";
    tag.style.font = fontProp;
    tag.innerHTML = text;

    document.body.appendChild(tag);

    var result = tag.clientWidth;

    document.body.removeChild(tag);

    return result;
}

用法:

if ( textWidth("Text", "bold 13px Verdana") > elementWidth) {
    ...
}

对于任何一个在那里使用React和/或Typescript…

试试这个Codepen!

export default function App() {
  const spanRef = useRef<HTMLSpanElement>(null);
  const [textWidth, setTextWidth] = useState(0);

  const getTextWidthInPixels = (ref: HTMLSpanElement) =>
    ref.getBoundingClientRect().width;

  useEffect(() => {
    setTextWidth(getTextWidthInPixels(spanRef.current!));
  }, [spanRef]);

  return (
    <div className="App">
      <span
        ref={spanRef}
        contentEditable
        suppressContentEditableWarning
        onInput={() => setTextWidth(getTextWidthInPixels(spanRef.current!))}
      >
        Edit Me!!!
      </span>
      {`textWidth: ${textWidth}px`}
    </div>
  );
}

将文本包装在内联定位的元素(如<span>)中是个好主意。 useRef是React访问DOM元素的方式，在我们的例子中是<span> getBoundingClientRect可以获得任何DOM元素的总宽度。 contentteditable允许用户更改元素的内容…这有点不安全(React会抛出警告!) suppresscontentteditablewarning将帮助我们防止这些警告

我喜欢你的“唯一的想法”只是做一个静态字符宽度地图!它实际上很适合我的目的。有时，出于性能原因，或者因为不容易访问DOM，您可能只想要一个快速的、独立的、校准为单一字体的计算器。这是一个用Helvetica字体校准的;传递一个字符串和字体大小:

const widths = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0.2796875,0.2765625,0.3546875,0.5546875,0.5546875,0.8890625,0.665625,0.190625,0.3328125,0.3328125,0.3890625,0.5828125,0.2765625,0.3328125,0.2765625,0.3015625,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.5546875,0.2765625,0.2765625,0.584375,0.5828125,0.584375,0.5546875,1.0140625,0.665625,0.665625,0.721875,0.721875,0.665625,0.609375,0.7765625,0.721875,0.2765625,0.5,0.665625,0.5546875,0.8328125,0.721875,0.7765625,0.665625,0.7765625,0.721875,0.665625,0.609375,0.721875,0.665625,0.94375,0.665625,0.665625,0.609375,0.2765625,0.3546875,0.2765625,0.4765625,0.5546875,0.3328125,0.5546875,0.5546875,0.5,0.5546875,0.5546875,0.2765625,0.5546875,0.5546875,0.221875,0.240625,0.5,0.221875,0.8328125,0.5546875,0.5546875,0.5546875,0.5546875,0.3328125,0.5,0.2765625,0.5546875,0.5,0.721875,0.5,0.5,0.5,0.3546875,0.259375,0.353125,0.5890625]
const avg = 0.5279276315789471

function measureText(str, fontSize) {
  return Array.from(str).reduce(
    (acc, cur) => acc + (widths[cur.charCodeAt(0)] ?? avg), 0
  ) * fontSize
}

这个巨大的丑陋数组是由字符代码索引的ASCII字符宽度。所以这只支持ASCII(否则它假设平均字符宽度)。幸运的是，宽度基本上是随字体大小线性缩放的，所以它在任何字体大小下都能很好地工作。它明显缺乏对字距或结扎之类的意识。

为了“校准”，我只是在svg上渲染了charCode 126(强大的波浪号)的每个字符，并获得了边界框并将其保存到这个数组中;这里有更多的代码、解释和演示。

如果有人在这里寻找一种测量字符串宽度的方法，以及一种知道适合特定宽度的最大字体大小的方法，这里有一个基于@Domi的解决方案的函数，使用二进制搜索:

/**
 * Find the largest font size (in pixels) that allows the string to fit in the given width.
 * 
 * @param {String} text - The text to be rendered.
 * @param {String} font - The css font descriptor that text is to be rendered with (e.g. "bold ?px verdana") -- note the use of ? in place of the font size.
 * @param {Number} width - The width in pixels the string must fit in
 * @param {Number} minFontPx - The smallest acceptable font size in pixels
 * @param {Number} maxFontPx - The largest acceptable font size in pixels
 **/
function GetTextSizeForWidth(text, font, width, minFontPx, maxFontPx) {
  for (;;) {
    var s = font.replace("?", maxFontPx);
    var w = GetTextWidth(text, s);
    if (w <= width) {
      return maxFontPx;
    }

    var g = (minFontPx + maxFontPx) / 2;

    if (Math.round(g) == Math.round(minFontPx) || Math.round(g) == Math.round(maxFontPx)) {
      return g;
    }

    s = font.replace("?", g);
    w = GetTextWidth(text, s);
    if (w >= width) {
      maxFontPx = g;
    } else {
      minFontPx = g;
    }
  }
}

如果你可以安装一个包，并且你想要一个更权威或更精确的答案，你可以使用opentype.js(奇怪的是没有人提到这一点):

import { load } from "opentype.js";

const getWidth = async (text = "Hello World") => {
  const font = await load("path/to/some/font");
  const { x1, x2 } = font.getPath(text, 0, 0, 12).getBoundingBox();
  return x2 - x1;
};

当然，您希望每个字体只调用load一次，因此应该根据您的情况将该行拉出到更高的范围。

下面是一个代码沙盒，将OpenType方法与Canvas和DOM方法进行比较: https://codesandbox.io/s/measure-width-of-text-in-javascript-vctst2

在我的机器上，每个100个样品，典型的结果是:

女士的OpenType: 5 女士帆布:3 女士DOM: 4

我发现的另一个软件包是:https://github.com/sffc/word-wrappr