start: function()

in bower_modules/backbone/backbone.js [1360:1421]

• 38 lines of code
• 21 McCabe index (conditional complexity)

    start: function(options) {
      if (History.started) throw new Error("Backbone.history has already been started");
      History.started = true;

      // Figure out the initial configuration. Do we need an iframe?
      // Is pushState desired ... is it available?
      this.options          = _.extend({root: '/'}, this.options, options);
      this.root             = this.options.root;
      this._wantsHashChange = this.options.hashChange !== false;
      this._wantsPushState  = !!this.options.pushState;
      this._hasPushState    = !!(this.options.pushState && this.history && this.history.pushState);
      var fragment          = this.getFragment();
      var docMode           = document.documentMode;
      var oldIE             = (isExplorer.exec(navigator.userAgent.toLowerCase()) && (!docMode || docMode <= 7));

      // Normalize root to always include a leading and trailing slash.
      this.root = ('/' + this.root + '/').replace(rootStripper, '/');

      if (oldIE && this._wantsHashChange) {
        this.iframe = Backbone.$('<iframe src="javascript:0" tabindex="-1" />').hide().appendTo('body')[0].contentWindow;
        this.navigate(fragment);
      }

      // Depending on whether we're using pushState or hashes, and whether
      // 'onhashchange' is supported, determine how we check the URL state.
      if (this._hasPushState) {
        Backbone.$(window).on('popstate', this.checkUrl);
      } else if (this._wantsHashChange && ('onhashchange' in window) && !oldIE) {
        Backbone.$(window).on('hashchange', this.checkUrl);
      } else if (this._wantsHashChange) {
        this._checkUrlInterval = setInterval(this.checkUrl, this.interval);
      }

      // Determine if we need to change the base url, for a pushState link
      // opened by a non-pushState browser.
      this.fragment = fragment;
      var loc = this.location;
      var atRoot = loc.pathname.replace(/[^\/]$/, '$&/') === this.root;

      // Transition from hashChange to pushState or vice versa if both are
      // requested.
      if (this._wantsHashChange && this._wantsPushState) {

        // If we've started off with a route from a `pushState`-enabled
        // browser, but we're currently in a browser that doesn't support it...
        if (!this._hasPushState && !atRoot) {
          this.fragment = this.getFragment(null, true);
          this.location.replace(this.root + this.location.search + '#' + this.fragment);
          // Return immediately as browser will do redirect to new url
          return true;

        // Or if we've started out with a hash-based route, but we're currently
        // in a browser where it could be `pushState`-based instead...
        } else if (this._hasPushState && atRoot && loc.hash) {
          this.fragment = this.getHash().replace(routeStripper, '');
          this.history.replaceState({}, document.title, this.root + this.fragment + loc.search);
        }

      }

      if (!this.options.silent) return this.loadUrl();
    },