Modifying background image with Javascript

Question

Modifying background image with Javascript

I've been working on developing a slideshow for one of the web pages I'm building. To achieve this, I set up a div with a unique class name that allows me to change the background image using JavaScript. Here's what I've accomplished so far:

Identified the specific div where I want to switch the background image using querySelector
Attempted to update the background image of that div using JavaScript

Despite debugging the function in DevTools, I'm still unable to figure out why the image isn't changing. Any insights on what might be going wrong? I've provided some code snippets below for reference. Appreciate any help.

HTML

<div class="content-one-right">
  <div class="inner-content-one-right">
    <div class="slideshow-container">
      <a class="prev" onclick="transitionSlides(-1)">&#10094;</a>
      <a class="next" onclick="transitionSlides(1)">&#10095;</a>
    </div>
  </div>
</div>

CSS

.content-one-right {
  grid-column: col-start 7 / span 6;
  height: 60vh;
}

.inner-content-one-right {
    height: 90%;
    width: 90%;
}

.slideshow-container {
    height: 100%;
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-image: url('../images/home-slideshow/home1.jpg');
    background-repeat: no-repeat;
    background-size: cover;
}

.prev, .next {
    cursor: pointer;
    color: #FFF;
    font-weight: bold;
    font-size: 1em;
    border-radius: 0 3px 3px 0;
}

.prev:hover, .next:hover {
    background-color: rgba(0,0,0,0.8);
}

JavaScript

var slideshowIndex = 0;

function transitionSlides(n) {

  var images = ["home1", "home2", "home3", "home4", "home5", "home6"];
  slideshowIndex += n;

  if(slideshowIndex < 0) {
    slideshowIndex = images.length-1;
  }
  else if (slideshowIndex >= images.length) {
    slideshowIndex = 0;
  }

  var getContainer = document.getElementsByClassName('slideshow-container')[0];
  var imageToChange = "url('../images/home-slideshow/" + images[slideshowIndex] + ".jpg')";

  getContainer.style.backgroundImage = imageToChange;

}

javascript css getelementsbyclassname

Answer 1

Answer №1

The issue may lie in the method you are employing to alter the background image. Initially, when you set it for the first time, it is done within the stylesheet using a CSS property.

Subsequently, when attempting to modify it using the .style property of the element, it proves ineffective as these methods differ. As stated on this page:

The style property does not provide a comprehensive view of the styles assigned to an element, only reflecting the CSS declarations established through inline styles rather than those derived from external style rules such as those present in the document's section or external style sheets.

To gain clarity, test this command in your console while on this current page:

document.querySelectorAll('input[type="submit"]')[3].style

This action targets the blue "Post Your Answer" button at the bottom of the page, featuring a clear blue background specified in the CSS. However, the CSSDeclaration object displayed in your console comprises solely of empty values because it exclusively represents the inline styles and not those applied via CSS.

Fascinating, isn't it? Armed with this understanding, I believe you can select between the two approaches to ensure your slideshow functions as anticipated. Perhaps avoiding the use of background images altogether might be simpler; opting instead for an img tag where JavaScript can be employed to configure the src attribute.

Answer 2

The issue may lie in the method you are employing to alter the background image. Initially, when you set it for the first time, it is done within the stylesheet using a CSS property.

Subsequently, when attempting to modify it using the .style property of the element, it proves ineffective as these methods differ. As stated on this page:

The style property does not provide a comprehensive view of the styles assigned to an element, only reflecting the CSS declarations established through inline styles rather than those derived from external style rules such as those present in the document's section or external style sheets.

To gain clarity, test this command in your console while on this current page:

document.querySelectorAll('input[type="submit"]')[3].style

This action targets the blue "Post Your Answer" button at the bottom of the page, featuring a clear blue background specified in the CSS. However, the CSSDeclaration object displayed in your console comprises solely of empty values because it exclusively represents the inline styles and not those applied via CSS.

Fascinating, isn't it? Armed with this understanding, I believe you can select between the two approaches to ensure your slideshow functions as anticipated. Perhaps avoiding the use of background images altogether might be simpler; opting instead for an img tag where JavaScript can be employed to configure the src attribute.

Answer 3

Answer №2

Encountering a familiar issue as shown in this thread. Valuable insights are available there. When experimenting with your code in JSFiddle, an exception is thrown: transitionSlides is not defined. It's advised to eliminate the onclick handler and utilize addEventListener() instead. While utilizing IDs for prev and next buttons is recommended, the following approach will suffice:

HTML:

<div class="content-one-right">
    <div class="inner-content-one-right">
        <div class="slideshow-container">
            <a class="prev">&#10094;</a>
            <a class="next">&#10095;</a>
        </div>
    </div>
</div>

JavaScript:

var slideshowIndex = 0;

document.getElementsByClassName('prev')[0].addEventListener("click", function() {
    transitionSlides(-1);
}, false);
document.getElementsByClassName('next')[0].addEventListener("click", function() {
    transitionSlides(1);
}, false);

function transitionSlides(n) {

    var images = ["home1", "home2", "home3", "home4", "home5", "home6"];
    slideshowIndex += n;

    if(slideshowIndex < 0) {
        slideshowIndex = images.length-1;
    }
    else if (slideshowIndex >= images.length) {
        slideshowIndex = 0;
    }

    var getContainer = document.getElementsByClassName('slideshow-container')[0];
    var imageToChange = "url('../images/home-slideshow/" + images[slideshowIndex] + ".jpg')";

    getContainer.style.backgroundImage = imageToChange;

}

Answer 4

Encountering a familiar issue as shown in this thread. Valuable insights are available there. When experimenting with your code in JSFiddle, an exception is thrown: transitionSlides is not defined. It's advised to eliminate the onclick handler and utilize addEventListener() instead. While utilizing IDs for prev and next buttons is recommended, the following approach will suffice:

HTML:

<div class="content-one-right">
    <div class="inner-content-one-right">
        <div class="slideshow-container">
            <a class="prev">&#10094;</a>
            <a class="next">&#10095;</a>
        </div>
    </div>
</div>

JavaScript:

var slideshowIndex = 0;

document.getElementsByClassName('prev')[0].addEventListener("click", function() {
    transitionSlides(-1);
}, false);
document.getElementsByClassName('next')[0].addEventListener("click", function() {
    transitionSlides(1);
}, false);

function transitionSlides(n) {

    var images = ["home1", "home2", "home3", "home4", "home5", "home6"];
    slideshowIndex += n;

    if(slideshowIndex < 0) {
        slideshowIndex = images.length-1;
    }
    else if (slideshowIndex >= images.length) {
        slideshowIndex = 0;
    }

    var getContainer = document.getElementsByClassName('slideshow-container')[0];
    var imageToChange = "url('../images/home-slideshow/" + images[slideshowIndex] + ".jpg')";

    getContainer.style.backgroundImage = imageToChange;

}

Modifying background image with Javascript

Answer №1

Answer №2

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