Fetches and resolves an image

fetchImage.js

/**
 * Fetches image and returns promise after fetch.
 *
 * @param {string} imageUrl -  Image SRC to fetch
 * @return {Promise} Returns promise of imageUrl that was successful
 */
export default function fetchImage(imageUrl) {
    return new Promise((resolve, reject) => {
        if (imageUrl == null) {
            reject('Image is null or undefined', imageUrl);
            return;
        }
        // Create New Image
        const downloadImage = new Image();
        downloadImage.onload = () => {
            // Resolve and return imageUrl once loaded.
            resolve(imageUrl);
        };

        downloadImage.onerror = (err) => {
            // Reject and return error and imageUrl if error.
            reject(err, imageUrl);
        };

        // Start the Download.
        downloadImage.src = imageUrl;
    });
}