Top questions with answers asked in MNC on Backbone.js

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Backbone.js interview questions along with their answers:

  1. What is Backbone.js, and what are its key components?
    • Answer: Backbone.js is a lightweight JavaScript framework used for building structured and maintainable web applications by providing the necessary infrastructure for organizing code, managing data, and synchronizing with the server. The key components of Backbone.js include:
      • Models: Represent data and business logic, providing an interface for interacting with data from the server or local storage.
      • Views: Render UI components and respond to user events, updating the interface based on changes to the underlying data.
      • Collections: Manage sets of models, providing methods for querying, filtering, and iterating over a group of related objects.
      • Routers: Handle navigation and URL routing, mapping URLs to application states and managing browser history.
  2. What is the role of Models in Backbone.js, and how are they defined?
    • Answer: Models in Backbone.js represent data entities and encapsulate business logic related to data manipulation, validation, and synchronization with the server. Models provide an interface for interacting with data from the server or local storage, such as creating, reading, updating, and deleting (CRUD) operations. In Backbone.js, models are defined by extending the Backbone.Model base class and specifying attributes and methods specific to the model. For example:

      javascript

      var Todo = Backbone.Model.extend({
      defaults: {
      title: '',
      completed: false
      },
      validate: function(attrs) {
      if (!attrs.title) {
      return 'Title is required';
      }
      }
      });
  3. What is the role of Views in Backbone.js, and how are they implemented?
    • Answer: Views in Backbone.js are responsible for rendering UI components, responding to user events, and updating the interface based on changes to the underlying data (models). Views encapsulate presentation logic and provide a separation of concerns between UI components and application logic. In Backbone.js, views are defined by extending the Backbone.View base class and implementing methods such as render() to generate HTML markup, events to define event handlers, and initialize() to set up the view. For example:

      javascript

      var TodoView = Backbone.View.extend({
      tagName: 'li',
      template: _.template($('#todo-template').html()),
      initialize: function() {
      this.listenTo(this.model, 'change', this.render);
      },
      render: function() {
      this.$el.html(this.template(this.model.toJSON()));
      return this;
      },
      events: {
      'click .toggle': 'toggleCompleted'
      },
      toggleCompleted: function() {
      this.model.set('completed', !this.model.get('completed'));
      }
      });
  4. What is the role of Collections in Backbone.js, and how are they used?
    • Answer: Collections in Backbone.js represent sets of models and provide methods for querying, filtering, and iterating over a group of related objects. Collections act as a container for managing multiple instances of a particular model type and provide a uniform interface for performing batch operations on models. Collections can be used to fetch data from the server, store data locally, or synchronize changes with a backend data source. In Backbone.js, collections are defined by extending the Backbone.Collection base class and specifying the model type. For example:

      javascript

      var Todos = Backbone.Collection.extend({
      model: Todo,
      url: '/todos'
      });      var todos = new Todos();
      todos.fetch();
  5. What is the role of Routers in Backbone.js, and how are they implemented?
    • Answer: Routers in Backbone.js are responsible for handling navigation and URL routing within a single-page web application. Routers map URLs to application states and manage browser history, enabling users to navigate between different views or sections of the application without reloading the page. Routers define routes using regular expressions and specify corresponding callback functions to execute when a route is matched. In Backbone.js, routers are defined by extending the Backbone.Router base class and implementing the routes object to define URL patterns and associated handler methods. For example:

      javascript

      var TodoRouter = Backbone.Router.extend({
      routes: {
      '': 'index',
      'todos/:id': 'show'
      },
      index: function() {
      // Show the list of todos
      },
      show: function(id) {
      // Show details of a specific todo
      }
      });      var router = new TodoRouter();
      Backbone.history.start();