使用JavaScript检测浏览器是否支持Web开放字体格式（Woff）

Question

我需要用JS（jQuery）检测浏览器是否支持Woff，并将类添加到body中。类似这样：

    if(woffIsSupported){

    $('body').addClass('modern');

    }

这是否有可能实现？感谢您的回答。

- user967165

---

为什么不直接添加样式，让CSS回退到某个默认字体，如果无法使用网络字体呢？ - Pointy

这种回退方案存在一些限制：例如，在使用自定义字体呈现图标时。在这种情况下的一个解决方法可能是使用 content CSS 属性（当然，这会违反内容和样式的分离）。 - try-catch-finally

我需要相同的功能。我的Web应用程序需要支持默认的Android 2.2浏览器，但它不使用回退TTF字体。（尝试加载WOFF而不是TTF字体 - 这种格式不受支持 - 结果所有文本都变得不可见。） - Tamás Bolvári

Answer 1

这篇文章中有一个名为 this post 的函数，名为 isFontFaceSupported，它会基于浏览器功能检查字体支持情况（好的方式，即不依赖用户代理字符串）。

复制该函数，您的代码可以变成：

if(isFontFaceSupported()) {
  $('body').addClass('modern');
}

---

这里是来自帖子的函数：

/*!
 * isFontFaceSupported - v0.9 - 12/19/2009
 * http://paulirish.com/2009/font-face-feature-detection/
 *
 * Copyright (c) 2009 Paul Irish
 * MIT license
 */

var isFontFaceSupported = (function(){


    var fontret,
        fontfaceCheckDelay = 100;

      // IE supports EOT and has had EOT support since IE 5.
      // This is a proprietary standard (ATOW) and thus this off-spec,
      // proprietary test for it is acceptable.
    if (!(!/*@cc_on@if(@_jscript_version>=5)!@end@*/0)) fontret = true;

    else {

    // Create variables for dedicated @font-face test
      var doc = document, docElement = doc.documentElement,
          st  = doc.createElement('style'),
          spn = doc.createElement('span'),
          wid, nwid, body = doc.body,
          callback, isCallbackCalled;

      // The following is a font, only containing the - character. Thanks Ethan Dunham.
      st.textContent = "@font-face{font-family:testfont;src:url(data:font/opentype;base64,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)}";
      doc.getElementsByTagName('head')[0].appendChild(st);


      spn.setAttribute('style','font:99px _,serif;position:absolute;visibility:hidden');

      if  (!body){
        body = docElement.appendChild(doc.createElement('fontface'));
      }

      // the data-uri'd font only has the - character
      spn.innerHTML = '-------';
      spn.id        = 'fonttest';

      body.appendChild(spn);
      wid = spn.offsetWidth;

      spn.style.font = '99px testfont,_,serif';

      // needed for the CSSFontFaceRule false positives (ff3, chrome, op9)
      fontret = wid !== spn.offsetWidth;

      var delayedCheck = function(){
        if (isCallbackCalled) return;
        fontret = wid !== spn.offsetWidth;
        callback && (isCallbackCalled = true) && callback(fontret);
      }

      addEventListener('load',delayedCheck,false);
      setTimeout(delayedCheck,fontfaceCheckDelay);
    }

    function ret(){  return fontret || wid !== spn.offsetWidth; };

    // allow for a callback
    ret.ready = function(fn){
      (isCallbackCalled || fontret) ? fn(fontret) : (callback = fn);
    }

    return ret;
})();

- Clive

---

这个问题是关于WOFF支持检测的。它检查@font-face是否被支持 - 如果我没错的话 - 这和检查WOFF是否被支持不同。检测isWOFFSupported是否可行？ - Tamás Bolvári

Answer 2

因为很难测试我只使用了浏览器检测：

//test ie 6, 7, 8
var div = document.createElement("div");
div.innerHTML = "<!--[if lte IE 8]><i></i><![endif]-->";
var isIe8orLower = !!div.getElementsByTagName("i").length;

if (!isIe8orLower && !navigator.userAgent.match(/Opera Mini/i)) {
    $('body').addClass('modern');
}

它匹配使用方式：http://caniuse.com/#feat=woff

- Tomas Randus