Extract the URL of the background image from a preexisting <div> element, or append a new attribute to the background-image property

Question

Extract the URL of the background image from a preexisting <div> element, or append a new attribute to the background-image property

I am facing a challenge in updating the existing background-image with a linear gradient. Currently, my CMS is generating a background-image, but I am unable to adjust the opacity using a linear gradient. My goal is to darken the background-image using CSS.

Here is my approach -> Extracting the URL from all div elements with the class of "bg-image" to then use the "setAttribute" method to apply a new background-image property.

   var elems = document.getElementsByClassName("bg-image");
    for (var i = 0, n = elems.length; i<n; ++i){
        var img = document.getElementsByClassName('bg-image')[i],
            bi = style.backgroundImage.slice(4, -1);

        img.setAttribute('style', 'background-image: linear-gradient( rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5),url("' bi +'"));');};

javascript jquery css background-image

Answer 1

Answer №1

Since you have tagged jQuery, I assume you are open to using it alongside vanilla JavaScript:

$(".bg-image").each({
    $(this).css({
        backgroundImage:"inear-gradient( rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5),"+$(this).css("backgroundImage"));
    });
});

Alternative approach without jQuery:

If you prefer using vanilla JavaScript, the issue lies in the line

bi = style.backgroundImage.slice(4, -1);

, which should likely be

bi = img.style.backgroundImage.slice(4, -1);

.

Moreover, avoid setting styles like this

img.setAttribute('style', 'background-image: linear-gradient( rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5),url("' bi +'"));')

Instead, use

img.style.backgroundImage="linear-gradient( rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5),url("+bi+")";

Since you are reintroducing it as a URL, there is no necessity to extract it using slice. Also, there is no need to reselect the element.

var elems = document.getElementsByClassName("bg-image");
for (var i = 0; i<elems.length; i++){
    var bi = elems[i].style.backgroundImage;
    elems[i].style.backgroundImage="linear-gradient( rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5),"+bi;
}

Answer 2

Since you have tagged jQuery, I assume you are open to using it alongside vanilla JavaScript:

$(".bg-image").each({
    $(this).css({
        backgroundImage:"inear-gradient( rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5),"+$(this).css("backgroundImage"));
    });
});

Alternative approach without jQuery:

If you prefer using vanilla JavaScript, the issue lies in the line

bi = style.backgroundImage.slice(4, -1);

, which should likely be

bi = img.style.backgroundImage.slice(4, -1);

.

Moreover, avoid setting styles like this

img.setAttribute('style', 'background-image: linear-gradient( rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5),url("' bi +'"));')

Instead, use

img.style.backgroundImage="linear-gradient( rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5),url("+bi+")";

Since you are reintroducing it as a URL, there is no necessity to extract it using slice. Also, there is no need to reselect the element.

var elems = document.getElementsByClassName("bg-image");
for (var i = 0; i<elems.length; i++){
    var bi = elems[i].style.backgroundImage;
    elems[i].style.backgroundImage="linear-gradient( rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0.5),"+bi;
}

Answer 3

Answer №2

You can achieve this effect without relying on javascript. Here's a Simple CSS approach:

The key idea is to utilize the :before selector to apply styling.

The implementation may vary depending on the structure of your background-styled HTML element, but you can utilize z-index to control the stacking order if needed (Alternatively, if the background image is set using CSS, you can apply it to #content:before, transfer the rgba to #content, making z-index adjustment unnecessary).

Feel free to check out the code snippet below to visualize the effect (I've added a red tint for visibility purposes).

#content {
  width: 400px;
  height: 200px;
  background: url("http://lorempixel.com/g/400/200/city/1/");
  position: relative;
  z-index: 1;
  color: white;
}
#content:before {
  content: "";
  position: absolute;
  z-index: 1;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  /* A gradient isn't necessary with this approach */
  background: rgba(255, 0, 0, 0.5);
}

<div id="content">
</div>

Answer 4

You can achieve this effect without relying on javascript. Here's a Simple CSS approach:

The key idea is to utilize the :before selector to apply styling.

The implementation may vary depending on the structure of your background-styled HTML element, but you can utilize z-index to control the stacking order if needed (Alternatively, if the background image is set using CSS, you can apply it to #content:before, transfer the rgba to #content, making z-index adjustment unnecessary).

Feel free to check out the code snippet below to visualize the effect (I've added a red tint for visibility purposes).

#content {
  width: 400px;
  height: 200px;
  background: url("http://lorempixel.com/g/400/200/city/1/");
  position: relative;
  z-index: 1;
  color: white;
}
#content:before {
  content: "";
  position: absolute;
  z-index: 1;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  /* A gradient isn't necessary with this approach */
  background: rgba(255, 0, 0, 0.5);
}

<div id="content">
</div>

Extract the URL of the background image from a preexisting <div> element, or append a new attribute to the background-image property

Answer №1

Answer №2

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