判断浏览器是否支持webp

1. 动态创建一个canvas元素，判断是否可以把canvas转为webp

0 === document.createElement('canvas').toDataURL('image/webp').indexOf('data:image/webp')

2.直接写一段简单的base64格式的webp字符串赋值给image的src，判断image是否有高度

const WebP = new Image();

    WebP.onload = function () {
        if (WebP.height > 0 && WebP.width > 0) {
            window.xx_supportWebp = 1;
        }
    };
    WebP.src = 'data:image/webp;base64,UklGRkoAAABXRUJQVlA4WAoAAAAQAAAAAAAAAAAAQUxQSAwAAAARBxAR/Q9ERP8DAABWUDggGAAAABQBAJ0BKgEAAQAAAP4AAA3AAP7mtQAAAA==';