How to Ensure a Background Image Loads Before Code Execution?

Ensuring Background Image Loading Before Code Execution

Incorporating a background image into the body tag and initiating subsequent code execution can pose a challenge when determining if the image has fully loaded. Using the conventional load() function, as seen in the provided example, won't suffice.

Solution:

To overcome this hurdle, consider the following approach:

$('<img  alt="How to Ensure a Background Image Loads Before Code Execution?" >').attr('src', 'http://picture.de/image.png').on('load', function() {
   $(this).remove(); // prevent memory leaks
   $('body').css('background-image', 'url(http://picture.de/image.png)');
});

This code creates a new image in memory, utilizing the load event to detect when the source image has been loaded. By removing the image after loading, potential memory leaks are avoided.

Vanilla JavaScript Implementation:

For vanilla JavaScript, the solution takes the following form:

var src = 'http://picture.de/image.png';
var image = new Image();
image.addEventListener('load', function() {
   body.style.backgroundImage = 'url(' + src + ')';
});
image.src = src;

Promise-Based Abstraction:

To abstract the process, a handy function can be created, returning a promise:

function load(src) {
    return new Promise((resolve, reject) => {
        const image = new Image();
        image.addEventListener('load', resolve);
        image.addEventListener('error', reject);
        image.src = src;
    });
}

const image = 'http://placekitten.com/200/300';
load(image).then(() => {
   body.style.backgroundImage = `url(${image})`;
});

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