This is an example of functional programming using JavaScript's built-in filter, map, and forEach functions. Note that this isn't a fully functional style as there are side effects.

selectAll.js

var selectAll = function() {
  views.filter(function(view) {
      if (view.$el.hasClass("active") !== toggle) {
          return true;
      }
  }).map(function(view) {
      return view.$el;
  }).forEach(function($el) {
      $el.toggleClass("active", toggle)
        .find("input:checkbox")
        .prop("checked", toggle);
  });
};