转载：轻量级浏览器特性检测库：feature.js

feature.js是一个很简单、快速和轻量级的浏览器特性检测库，它没有任何依赖，体积压缩最后只有1KB，它可以自动初始化，在你需要知道某个特性是否可用时，直接引入即可。以下中文为个人理解。

/*!
 * FEATURE.JS 1.0.0, A Fast, simple and lightweight browser feature
 * detection library in just 1kb.
 *
 * http://featurejs.com
 *
 * CSS 3D Transform, CSS Transform, CSS Transition, Canvas, SVG,
 * addEventListener, querySelectorAll, matchMedia, classList API,
 * placeholder, localStorage, History API, Viewport Units, REM Units,
 * CORS, WebGL, Service Worker, Context Menu, Geolocation,
 * Device Motion, Device Orientation, Touch, Async, Defer,
 * Srcset, Sizes & Picture Element.
 *
 *
 * USAGE EXAMPLE:
 * if (feature.webGL) {
 *   console.log("webGL supported!");
 * }
 *
 * Author: @viljamis, https://viljamis.com
 */

/* globals DocumentTouch */
;(function (window, document, undefined) {
  "use strict";

  // For minification only
  var docEl = document.documentElement;

  /**
   * Utilities
   */
  var util = {

    /**
     * Simple create element method
     */
    create : function(el) {
      return document.createElement(el);
    },

    /**
     * Test if it's an old device that we want to filter out
     */
    old : !!(/(Android\s(1.|2.))|(Silk\/1.)/i.test(navigator.userAgent)),

    /**
     * Function that takes a standard CSS property name as a parameter and
     * returns it's prefixed version valid for current browser it runs in
     * 返回当前的css属性是否当前运行的浏览器，例如一个css属性transition，这个函数会遍历
     * dummy.style['transition']/dummy.style["WebkitTransition"]/dummy.style["MozTransition"]/dummy.style["OTransition"]/dummy.style["msTransition"]
     * 的值是否为true，是则返回该值
     */
    pfx : (function() {
      var style = document.createElement("dummy").style;
      var prefixes = ["Webkit", "Moz", "O", "ms"];
      var memory = {};
      return function(prop) {
        if (typeof memory[prop] === "undefined") {
          var ucProp = prop.charAt(0).toUpperCase() + prop.substr(1),
            props = (prop + " " + prefixes.join(ucProp + " ") + ucProp).split(" ");
            memory[prop] = null;
          for (var i in props) {
            if (style[props[i]] !== undefined) {
              memory[prop] = props[i];
              break;
            }
          }
        }
        return memory[prop];
      };
    })()

  };

  /**
   * The Feature.js object
   *
   * @constructor
   */
  function Feature() {}

  Feature.prototype = {
    constructor : Feature,

    // Test if CSS 3D transforms are supported
    css3Dtransform : (function() {
      var test = (!util.old && util.pfx("perspective") !== null);
      return !!test;
    })(),

    // Test if CSS transforms are supported
    cssTransform : (function() {
      var test = (!util.old && util.pfx("transformOrigin") !== null);
      return !!test;
    })(),

    // Test if CSS transitions are supported
    // 检测css transition属性是否支持
    cssTransition : (function() {
      var test = util.pfx("transition") !== null;
      return !!test;
    })(),

    // Test if addEventListener is supported
    // 检测 addEventListener是否支持
    addEventListener : !!window.addEventListener,

    // Test if querySelectorAll is supported
    // 检测querySelectorAll是否支持
    querySelectorAll : !!document.querySelectorAll,

    // Test if matchMedia is supported
    // 检测媒体查询(media）是否支持
    matchMedia : !!window.matchMedia,

    // Test if Device Motion is supported
    // 检测device Motion是否支持
    deviceMotion : ("DeviceMotionEvent" in window),

    // Test if Device Orientation is supported
    deviceOrientation : ("DeviceOrientationEvent" in window),

    // Test if Context Menu is supported
    contextMenu : ("contextMenu" in docEl && "HTMLMenuItemElement" in window),

    // Test if classList API is supported
    // 检测classList是否支持
    classList : ("classList" in docEl),

    // Test if placeholder attribute is supported
    // 检测placeholder是否支持
    placeholder : ("placeholder" in util.create("input")),

    // Test if localStorage is supported
    localStorage : (function() {
      var test = "x";
      try {
        localStorage.setItem(test, test);
        localStorage.removeItem(test);
        return true;
      } catch(err) {
        return false;
      }
    })(),

    // Test if History API is supported
    historyAPI : (window.history && "pushState" in window.history),

    // Test if ServiceWorkers are supported
    serviceWorker : ("serviceWorker" in navigator),

    // Test if viewport units are supported
    viewportUnit : (function(el) {
      try {
        el.style.width = "1vw";
        var test = el.style.width !== "";
        return !!test;
      } catch(err) {
        return false;
      }
    })(util.create("dummy")),

    // Test if REM units are supported
    remUnit : (function(el) {
      try {
        el.style.width = "1rem";
        var test = el.style.width !== "";
        return !!test;
      } catch(err) {
        return false;
      }
    })(util.create("dummy")),

    // Test if Canvas is supported
    canvas : (function(el) {
      return !!(el.getContext && el.getContext("2d"));
    })(util.create("canvas")),

    // Test if SVG is supported
    svg : !!document.createElementNS && !!document.createElementNS("http://www.w3.org/2000/svg", "svg").createSVGRect,

    // Test if WebGL is supported
    webGL : (function(el) {
      try {
        return !!(window.WebGLRenderingContext && (el.getContext("webgl") || el.getContext("experimental-webgl")));
      } catch(err) {
        return false;
      }
    })(util.create("canvas")),

    // Test if cors is supported
    cors : ("XMLHttpRequest" in window && "withCredentials" in new XMLHttpRequest()),

    // Tests if touch events are supported, but doesn't necessarily reflect a touchscreen device
    touch : !!(("ontouchstart" in window) || window.navigator && window.navigator.msPointerEnabled && window.MSGesture || window.DocumentTouch && document instanceof DocumentTouch),

    // Test if async attribute is supported
    async : ("async" in util.create("script")),

    // Test if defer attribute is supported
    defer : ("defer" in util.create("script")),

    // Test if Geolocation is supported
    geolocation : ("geolocation" in navigator),

    // Test if img srcset attribute is supported
    srcset : ("srcset" in util.create("img")),

    // Test if img sizes attribute is supported
    sizes : ("sizes" in util.create("img")),

    // Test if Picture element is supported
    pictureElement : ("HTMLPictureElement" in window),

    // Run all the tests and add supported classes
    //查找在该对象中所有不是testAll、不是对象引用并且结果为true的方法，存进classes,最后输出来
    testAll : function() {
      var classes = " js";
      for (var test in this) {
        if (test !== "testAll" && test !== "constructor" && this[test]) {
          classes += " " + test;
        }
      }
      docEl.className += classes.toLowerCase();
    }

  };

  /**
   * Expose a public-facing API
   */
  function expose() {
    var ftr = new Feature();
    return ftr;
  }
  window.feature = expose();

}(window, document));

总体只有1KB，可以快速检测当前浏览器是否支持css3的特性。

使用方法：

if (feature.webGL) {
  console.log("WebGL supported");
} else {
  console.log("WebGL not supported");
}

属性列表：

Below you’ll find a list of all the available browser feature tests and how to call them.

feature.async
feature.addEventListener
feature.canvas
feature.classList
feature.cors
feature.contextMenu
feature.css3Dtransform
feature.cssTransform
feature.cssTransition
feature.defer
feature.deviceMotion
feature.deviceOrientation
feature.geolocation
feature.historyAPI
feature.placeholder
feature.localStorage
feature.matchMedia
feature.pictureElement
feature.querySelectorAll
feature.remUnit
feature.serviceWorker
feature.sizes
feature.srcset
feature.svg
feature.touch
feature.viewportUnit
feature.webGL

演示：

• Official site with live tests: http://featurejs.com
• Test with actual features: http://featurejs.com/test

原文链接：轻量级浏览器特性检测库：feature.js 版权所有，转载时请注明出处，违者必究。
注明出处格式：前端开发博客 (http://caibaojian.com/feature-js.html)