Question

如果未定义CSS font-face和font-size属性，如何获取元素的实际字体和字体大小？

例如，JavaScript代码段

object.style.fontFamily

不会返回任何值。这很明显，假设CSS没有在任何地方将样式应用于object。但是，当然，使用某种字体来渲染文本，可能是系统字体或webbrowser默认字体。

例如，JavaScript可以获得呈现的字体吗？

Answer 1

没有标准，可靠的方法来确定使用的实际字体。此前的答案将报告样式的 fontFamily 样式值，但这可以是字体名称列表，并不具体标识呈现的实际字体（这是< em>实际的问题在这里提出。）

（正如在一些评论中所提到的，通过检查视觉线索，有很多方法可以<\ n>猜测字体，但这可能不是100％可靠。）

Answer 2

我建议这个功能：

function css( element, property ) {
    return window.getComputedStyle( element, null ).getPropertyValue( property );
}

用法：

css( object, 'font-size' ) // returns '16px' for instance

注意：getComputedStyle在IE8中不起作用。

现场演示： http://jsfiddle.net/4mxzE/

Answer 3

您可以在Chrome / Firefox开发者工具中找到有关渲染字体的信息。请尝试检查以下代码段中的段落：

p { font-family: sans-serif;  }

<p>Some text and <span title="an emoji"></span></p>

在Chrome开发者工具中（在55.0.2883.75 m 64位上测试），您将获得以下信息：

在Firefox开发者工具中（在47.0.2上使用about:config > devtools.fontinspector.enabled = true测试），您将获得以下信息：

Answer 4

我找到了一种方法（适用于所有支持<canvas>的浏览器），如果字体渲染已更改，则通过检查像素为像素

function renderedfont(ele) {
    var getDefaultFonts = function () {
        var iframe = document.createElement('iframe');
        var html = '<html><body>';
        var fonts;
        document.body.appendChild(iframe);
        iframe.contentWindow.document.open();
        iframe.contentWindow.document.write(html);
        var subele = iframe.contentWindow.document.createElement(ele.tagName);
        iframe.contentWindow.document.body.appendChild(subele);
        fonts = getComputedStyle(subele)['font-family'];
        document.body.removeChild(iframe);
        return fonts;
    }
    var fonts = getComputedStyle(ele)['font-family'] + ',' + getDefaultFonts();
    var fontsArray = fonts.split(',');
    var canvas = document.createElement('canvas');
    var ctx = canvas.getContext("2d");
    var testString = "abcdefghijklmnopqrstuvwxyz!@#$%^&*()ñ";
    var prevImageData;
    document.body.appendChild(canvas);
    canvas.width = 500;
    canvas.height = 300;
    fontsArray.unshift('"Font That Doesnt Exists ' + Math.random() + '"');

    for (var i = 0; i < fontsArray.length; i++) {
        var fontName = fontsArray[i].trim();
        ctx.clearRect(0, 0, canvas.width, canvas.height);
        ctx.font = '16px ' + fontName + ', monospace';
        ctx.fillText(testString, 10, 100);
        var idata = ctx.getImageData(0, 0, canvas.width, canvas.height); 
        var data = idata.data
        if (prevImageData) {
            for (var j = 0; j < data.length; j += 3) {
                if (prevImageData[j + 3] !== data[j + 3]) {
                    document.body.removeChild(canvas);
                    return fontName;
                }
            }
        }
        prevImageData = data;
    }

    document.body.removeChild(canvas);
    return 'monospace';
}

所以要用你做：

renderedfont(document.body);
// Arial

如果您将其用于其他方言（例如日语），您可能需要将testString变量更改为该方言中最常见的字符。

Answer 5

在这里有点晚了，但是不得不解决同样的问题... ŠimeVidas的回答基本上是正确的，但如今，您可以发挥创造力并获得答案。

基本上，定义您自己的字体，确定与任何现有字体都不匹配。然后，在每种计算样式字体之后添加字体，然后查看是否是呈现的字体。否则，恭喜，您找到了呈现的字体

这是小提琴： https://jsfiddle.net/obutjanw/

这是定义所需功能的代码：

    (function(win) {

        var style = null;
        function createClass(name,rules){
            if (typeof(rules)!="string") {
                rules = JSON.stringify(rules).trim();
            }

            if (rules.startsWith("{")&&rules.endsWith("}")) {
                rules = rules.substring(1,rules.length-1);
            }

            if (style==null) {
                style = document.createElement('style');
                style.type = 'text/css';
                var head = document.getElementsByTagName('head');
                if (head.length=0) {
                    var h = document.createElement('head');
                    document.insertBefore(h,document.body);
                    head = [h];
                }
                head[0].appendChild(style);
            }


            var rule;
            if(!(style.sheet||{}).insertRule) {
                rule = (style.styleSheet || style.sheet).addRule(name, rules);
            } else {
                style.sheet.insertRule(name+"{"+rules+"}",0);
                rule = style.sheet
            }
            return rule;
        }

        function removeNode(node) {
            if (node.remove) {
                node.remove();
            } else {
                var pn = node.parentElement;
                if (pn!=null) {
                    pn.removeChild(node);
                }
            }
        }



        createClass("@font-face", "{ font-family: 'void';  src: url(data:application/font-woff2;charset=utf-8;base64,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) format('woff2'), url(data:application/font-woff;charset=utf-8;base64,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) format('woff'); }");


        var tests = document.createElement("span");
        tests.innerHTML = "0123";
        tests.style.display = "inline-block";
        tests.style.fontFamily = "void";
        document.body.appendChild(tests);
        setTimeout(function() {
            removeNode(tests);
        },0);

        function getRenderedFontFamily(elm, computedstyle) {
            var cs = (typeof(computedstyle) == 'undefined') ? win.getComputedStyle(elm) : computedstyle;
            var fontF   = (cs.fontFamily        || elm.style['font-family'] || '').replace(/['"]*/g, '');
            var tfontF = fontF.split(",");
            var tests = document.createElement("span");
            tests.innerHTML = "0123";
            tests.style.display = "inline-block";
            tests.style.fontFamily = "void";
            elm.appendChild(tests);
            var refcs = window.getComputedStyle(tests);
            var refw = refcs.width;
            var tested = {};
            while (tfontF!=null) {
                for (var i=0;i<tfontF.length;i++) {
                    if (tested[tfontF[i]]) continue;
                    tests.style.fontFamily = tfontF[i] + ", void";
                    if (refcs.width!=refw) {
                        removeNode(tests);
                        return tfontF[i].trim();
                    }
                    tested[tfontF[i]] = true;
                }
                if (elm.parentElement) {
                    elm = elm.parentElement;
                    var cs1 = win.getComputedStyle(elm);
                    fontF   = (cs1.fontFamily       || elm.style['font-family'] || '').replace(/['"]*/g, '');
                    tfontF = fontF.split(",");
                } else {
                    tfontF = null;
                }
            }
            removeNode(tests);
        }
        win.getRenderedFontFamily =  getRenderedFontFamily;
    })(window);

请注意，您确实应该保持零件是使用加载时附加字体的节点，否则浏览器可能会在第一次调用getRenderedFontFamily时延迟渲染corect字体

如何在CSS中未定义实际渲染字体？

5 个答案: