freeCodeCamp/guide/english/miscellaneous/guide-to-build-a-sliding-image-gallery/index.md

---
title: Guide to Build a Sliding Image Gallery
---
This tutorial will walk you through building an image slider using the <a href='https://jquery.com/' target='_blank' rel='nofollow'>jQuery</a> library.

[![GIF showing Slider in action](//discourse-user-assets.s3.amazonaws.com/original/2X/0/08d83a22c28da836a06853b1f1ea669b398326b9.gif)](https://codepen.io/atjonathan/pen/BKMxxq)

This tutorial will have four parts:  
- [HTML](#html)  
- [SCSS](#scss)  
- [JS](#js)  
- [References](#references)

## HTML

We will be using <a href='http://getbootstrap.com/' target='_blank' rel='nofollow'>Bootstrap</a> for this tutorial to keep things looking good, without spending a lot of time.

Our structure will be as follows:

    <div class="container">

      <!-- The wrapper for our slider -->
      <div class="slider">
        <ul class="slides"><!-- Each image will be inside this unordered list --></ul>
      </div>

      <div class="buttons"><!-- Pause and play buttons will go in here --></div>

    </div>

Inside our `ul` with the class of `slides` we will have the following:

    <li class="slide"><img src="#" /></li>
    <li class="slide"><img src="#" /></li>
    <li class="slide"><img src="#" /></li>
    <li class="slide"><img src="#" /></li>
    <li class="slide"><img src="#" /></li>

Inside our `.buttons` class you should have the following:

    <button type="button" class="btn btn-default pause">
    	<span class="glyphicon glyphicon-pause"></span>
    </button>
    <button type="button" class="btn btn-default play">
    	<span class="glyphicon glyphicon-play"></span>
    </button>

Here is an example of what your `html` should look like:

> Note: You should replace the image `src` attribute with your own content.

    <div class="container">

      <div class="slider">
        <ul class="slides">
          <li class="slide"><img src="https://unsplash.it/1280/720/?image=120" /></li>
          <li class="slide"><img src="https://unsplash.it/1280/720/?image=70" /></li>
          <li class="slide"><img src="https://unsplash.it/1280/720/?image=50" /></li>
          <li class="slide"><img src="https://unsplash.it/1280/720/?image=170" /></li>
          <li class="slide"><img src="https://unsplash.it/1280/720/?image=190" /></li>
        </ul>
      </div>

      <div class="buttons">
        <button type="button" class="btn btn-default pause">
          <span class="glyphicon glyphicon-pause"></span>
        </button>
        <button type="button" class="btn btn-default play">
          <span class="glyphicon glyphicon-play"></span>
        </button>
      </div>

    </div>

## SCSS

We are using <a href='http://sass-lang.com/' target='_blank' rel='nofollow'>Sass</a> and the SCSS syntax so we can nest and use variables ![:heart_decoration:](//forum.freecodecamp.com/images/emoji/emoji_one/heart_decoration.png?v=2 ":heart_decoration:")

We can use the following SCSS to define our styling:

    // Variables
    $width: 720px;

    .slider {
      width: $width;
      height: 400px;
      overflow: hidden;
      margin: 0 auto;
      text-align: center;

      .slides {
        display: block;
        width: 6000px;
        height: 400px;
        margin: 0;
        padding: 0;
      }

      .slide {
        float: left;
        list-style-type: none;
        width: $width;
        height: 400px;

        img {
          width: 100%;
          height: 100%;
        }
      }
    }

    .buttons {
      margin: 0;
      width: $width;
      position: relative;
      top: -40px;
      margin: 0 auto;

      .play {
        display: none;
      }

      .btn {
        display: flex;
        margin: 0 auto;
        text-align: center;
      }
    }

## JS

#### Variables

_In the following code snippet, we define variables used later in our code._

    var animationSpeed = 1000; // How quickly the next slide animates.
    var pause = 3000; // The pause between each slide.

We will use a blank variable where we will call the `setInterval` method:  

    var interval;

#### Animation We will wrap our slider animations inside a function:  

    function startSlider() {}

We are using the `setInterval()` native JavaScript method to automate the contents of the function on a time based trigger.  

    interval = setInterval(function() {}, pause);

We use the `pause` variable to see how many milliseconds to wait before calling the function again. Read more on the native `setInterval` method here: https://developer.mozilla.org/en-US/docs/Web/API/WindowTimers/setInterval. Inside our function we will use jQuery to fade between slides at the speed of the animationSpeed variable:  

    $('.slides > li:first')
      .fadeOut(animationSpeed)
      .next()
      .fadeIn(animationSpeed)
      .end()
      .appendTo('.slides');

- We are targeting the first slide using `$('.slides > li:first')`. - `.fadeOut(animationSpeed)` will fade the first slide out and then using `.next()`, we move to the next slide. - Once we have moved to the next slide, we will fade it in: `.fadeIn(animationSpeed)`. - This sequence will continue until the last slide (`.end()`), then we stop the animation. We will now call the `startSlider` function to start the animation:  

    startSlider();

#### Play and Pause *This feature is optional, but quite easy to implement.* We will hide the play button, so we don't see both the play and pause buttons:  

    $('.play').hide(); // Hiding the play button.

We will now create our pause button (automatically shown on page load):  

    $('.pause').click(function() {
    	clearInterval(interval);
    	$(this).hide();
    	$('.play').show();
    });

- We will call our function every time the pause button is clicked using jQuery. - We will remove the interval using the `clearInterval` method and using our `interval` variable as the parameter, indicating which interval to stop. - Because our slider is paused, we will hide the pause button using `$(this).hide();`. Note: we are using `this`, which will refer to what our parent is calling i.e. `.pause`. - We will then show our play button so the user can resume the animation: `$('.play').show();`. The following code sets up our play button (automatically hidden on page load):  

    $('.play').click(function() {
    	startSlider();
    	$(this).hide();
    	$('.pause').show();
    });

*   We will call our function every time the play button is clicked using jQuery.
    *   We will start or restart the interval using the `startSlider` function.
    *   Because our slider is currently playing, we will hide the play button using `$(this).hide();`. Note: we are using `this`, which will refer to what our parent is calling i.e. `.play`.
    *   We will then show our pause button so the user can stop the animation at will: `$('.pause').show();`.

## References

*   Checkout the source code and example on <a href='https://codepen.io/atjonathan/pen/BKMxxq' target='_blank' rel='nofollow'>CodePen</a> for this tutorial.