/**
   * Module exports.
   */
  
  module.exports = deprecate;
  
  /**
   * Mark that a method should not be used.
   * Returns a modified function which warns once by default.
   *
   * If `localStorage.noDeprecation = true` is set, then it is a no-op.
   *
   * If `localStorage.throwDeprecation = true` is set, then deprecated functions
   * will throw an Error when invoked.
   *
   * If `localStorage.traceDeprecation = true` is set, then deprecated functions
   * will invoke `console.trace()` instead of `console.error()`.
   *
   * @param {Function} fn - the function to deprecate
   * @param {String} msg - the string to print to the console when `fn` is invoked
   * @returns {Function} a new "deprecated" version of `fn`
   * @api public
   */
  
  function deprecate (fn, msg) {
    if (config('noDeprecation')) {
      return fn;
    }
  
    var warned = false;
    function deprecated() {
      if (!warned) {
        if (config('throwDeprecation')) {
          throw new Error(msg);
        } else if (config('traceDeprecation')) {
          console.trace(msg);
        } else {
          console.warn(msg);
        }
        warned = true;
      }
      return fn.apply(this, arguments);
    }
  
    return deprecated;
  }
  
  /**
   * Checks `localStorage` for boolean values for the given `name`.
   *
   * @param {String} name
   * @returns {Boolean}
   * @api private
   */
  
  function config (name) {
    // accessing global.localStorage can trigger a DOMException in sandboxed iframes
    try {
      if (!global.localStorage) return false;
    } catch (_) {
      return false;
    }
    var val = global.localStorage[name];
    if (null == val) return false;
    return String(val).toLowerCase() === 'true';
  }