detect.js

module.exports = function (target, prefixes) {
  var prefixIdx;
  var prefix;
  var testName;
  var scope = this || window;

  // initialise to default prefixes
  // (reverse order as we use a decrementing for loop)
  prefixes = (prefixes || ['ms', 'o', 'moz', 'webkit']).concat('');

  // iterate through the prefixes and return the class if found in global
  for (prefixIdx = prefixes.length; prefixIdx--;) {
    prefix = prefixes[prefixIdx];

    // construct the test class name
    // if we have a prefix ensure the target has an uppercase first character
    // such that a test for getUserMedia would result in a search for
    // webkitGetUserMedia
    testName = prefix + (prefix ?
      target.charAt(0).toUpperCase() + target.slice(1) :
      target);

    if (typeof scope[testName] == 'function' || typeof scope[testName] == 'object') {
      return scope[testName];
    }
  }
};