check-webp.js

function check_webp_feature(feature = 'lossy') {
    var kTestImages = {
        lossy: 'UklGRiIAAABXRUJQVlA4IBYAAAAwAQCdASoBAAEADsD+JaQAA3AAAAAA',
        lossless: 'UklGRhoAAABXRUJQVlA4TA0AAAAvAAAAEAcQERGIiP4HAA==',
        alpha: 'UklGRkoAAABXRUJQVlA4WAoAAAAQAAAAAAAAAAAAQUxQSAwAAAARBxAR/Q9ERP8DAABWUDggGAAAABQBAJ0BKgEAAQAAAP4AAA3AAP7mtQAAAA==',
        animation:
            'UklGRlIAAABXRUJQVlA4WAoAAAASAAAAAAAAAAAAQU5JTQYAAAD/////AABBTk1GJgAAAAAAAAAAAAAAAAAAAGQAAABWUDhMDQAAAC8AAAAQBxAREYiI/gcA'
    }
    return new Promise((resolve, reject) => {
        var img = new Image()
        img.onload = () => resolve(img.width > 0 && img.height > 0)
        img.onerror = () => reject(false)
        img.src = 'data:image/webp;base64,' + kTestImages[feature]
    })
}