Is WEBP supported

index.js

let webpSupported = undefined;

/* export ES6+ */ async function isWebpSupported() {
    if (webpSupported !== undefined) {
        return webpSupported;
    }

    const promise = new Promise(resolve => {
        const image = new Image();
        image.onload = function () {
            resolve(image.width === 2 && image.height === 1);
        }
        image.onerror = function () {
            resolve(false);
        }
        image.src = 'data:image/webp;base64,UklGRjIAAABXRUJQVlA4ICYAAACyAgCdASoCAAEALmk0mk0iIiIiIgBoSygABc6zbAAA/v56QAAAAA==';
    });

    return webpSupported = await promise;
}