The Swapper will display the tweet sections of our app. To build it out, we will create three modules --Swapper, Sections, and Tweets-- each of which will contain its own class. Similar to our Footer, we will create the parent Swapper class first and then work our way down to the child classes.



Like our Header and Footer, we will create a Swapper class and export it as a module. The Swapper will show the current section and keep the other sections off the screen.

Open up Swapper.js and add the code below.

var data = require('./Data');
var Section = require('./Section');
var Node = require('famous/core/Node');
var Align = require('famous/components/Align');
var DOMElement = require('famous/dom-renderables/DOMElement');

// The swapper will hold the sections and swap between them
// on events
function Swapper () {
    // subclass Node

    // create a new dom element 
    this.el = new DOMElement(this);

    // store the current section
    this.currentSection = null;

    // create the sections
    this.sections = createSections.call(this);

// subclass Node
Swapper.prototype = Object.create(Node.prototype);

module.exports = Swapper;

As you can see above, we add our sections through an external function called createSections. Using the lines below, let's build a createSections function.

function createSections () {
    var result = {};

    // iterate over all the sections in our data
    data.sections.forEach(function (section, i) {
        var child = this.addChild();
        result[section.id] = {
            align: new Align(child),
            section: child.addChild(new Section(i))

    return result;

Modified files: Swapper.js

The code above creates a node, Align component, and Section instance for each section in the data. Now, let's create the Section class so the code above will run.


Open up Section.js and include the code below to create our Section module.

var data = require('./Data');
var Node = require('famous/core/Node');
var DOMElement = require('famous/dom-renderables/DOMElement');
var Tweet = require('./Tweet');

function Section (i) {
    // subclass Node

    // create and style a new DOMElement
    this.el = new DOMElement(this).setProperty('overflow-y', 'scroll')
                                  .setProperty('overflow-x', 'hidden');

    // create the tweets in the section.
    this.tweets = createTweets.call(this, i);

Section.prototype = Object.create(Node.prototype);

function createTweets (id) {
    var result = [];
    var numberOfTweets = data.sections[id].tweetNumber;
    var tweet;

    // create an array of length equal to the number of tweets and then
    // map over it to create an array of tweets
    for (var i = 0 ; i < numberOfTweets ; i++) {
        // this node will be 100px tall and positioned after the previous one
        // in the array
        tweet = this.addChild()
                    .setSizeMode('default', 'absolute')
                    .setAbsoluteSize(null, 100)
                    .setPosition(0, 100 * i)
                    .addChild(new Tweet());


    return result;

module.exports = Section;

Modified files: Section.js

Note how we use the createTweets function to build our Tweets in the same way we did for our sections in the previous step. Within the function, each tweet is sized and positioned one after another 100px down. Now let's move on to the Tweets class and module.


Add the code below to Tweets.js to create our tweets module.

var Node = require('famous/core/Node');
var DOMElement = require('famous/dom-renderables/DOMElement');
var data = require('./Data');

// The tweet class that will render a particular tweet
function Tweet () {
    // subclass Node

    // create a new DOMElement and style it.
    this.el = new DOMElement(this).setProperty('backgroundColor', getRandomColor())
                                  .setProperty('boxSizing', 'border-box')
                                  .setProperty('lineHeight', '100px')
                                  .setProperty('borderBottom', '1px solid black')
                                  .setProperty('font-size', '12px')

// subclass Node
Tweet.prototype = Object.create(Node.prototype);

// Pick a random element from an array
function random (array) {
    return array[(Math.random() * array.length)|0];

// create Random message
function getRandomMessage () {
    return '<b>' + random(data.usernames) +
           ':</b>' + random(data.begin) + random(data.middle) + random(data.end) +
           ' ' + random(data.hashtags) + ' ' + random(data.hashtags);

// Create a random hex color
function getRandomColor() {
    // trick to create a range.
    return '#' + Array.apply(null, Array(6)).map(function (_, i) {
        return random('0123456789ABCDEF');

module.exports = Tweet;

Above, you'll see we call two functions --getRandomColor() and getRandomMessage()-- to generate and style random tweets. These functions use data that will be added to Data.json. Here is Data.json:

// Holds the data for the application

    sections: [{
        id: 'Home',
        tweetNumber: 50
    }, {
        id: 'Discover',
        tweetNumber: 50
    }, {
        id: 'Connect',
        tweetNumber: 50
    }, {
        id: 'Me',
        tweetNumber: 25

    usernames: ['@LouieBlooRaspberry','@PonchoPunch','@SirIsaacLime','@StrawberryShortKook','@AlexandertheGrape', '@LittleOrphanOrange'],
    begin: ['Walk towards ', 'Jump on ' ,'Sing to ', 'Dance with ', 'Stare down ', 'Pick up ', 'Hold hands with ', 'Walk around ', 'Shake hands with ', 'Talk to ', 'Point at ', 'Read to ', 'High five ', 'Wave to ' ],
    middle: ['a duck ', 'some fish ', 'a zebra ', 'nine honey badgers ', 'an old gorilla ', 'a ham sandwich ', 'a peanut ', 'Nicolas Cage ', 'a sock ', 'a pillow ', '12 fish ','a potato ', 'your neighbor ', 'a snail '],
    end: ['quickly','and don\'t look back','without shoes', 'and clap your hands', 'and pat your belly', 'and do a jig', 'tomorrow', 'while eating ice cream', 'in the dark', 'at the park', 'with a friend', 'down by the bay', 'in the car', 'and yell'],
    hashtags: ['#harrystyles', '#live', '#boredom', '#mylife', '#hiphop', '#texas', '#november', '#scary', '#best',' #snowman', '#shuffle', '#squats', '#selfie' ]


Now that we have all of our classes built, we are ready to bring it all together and add a Swapper instance to Twitterus.

Modified files: Tweet.js

Adding the Swapper

In order to reference the Swapper class in Twitterus, we will need to import the module using the following line.

var Swapper = require('./Swapper')

Once it's imported at top, create a new instance of Swapper in the function makeSwapper().

// make the swapper
function makeSwapper (node) {
    // the swapper will be 200 pixels smaller than
    // its parent in Y and otherwise the same size.
    // It will be position 100 pixels below its parent
    // such that it clears the header
        .setDifferentialSize(null, -200, null)
        .setPosition(0, 100)
        .addChild(new Swapper());

In the next, section we will make our app respond to user interaction through 'clicks'.

Modified files: Twitterus.js

Section recap: Code for this step

Up Next: User Interaction »