uniapp H5保存base64图片方法

                         savePicture(base64) {  

            // var arr = base64.split(','); //可以这样去掉data:image/png;base64,只拿，号后面部分  
            var bytes = atob(base64)  
            let ab = new ArrayBuffer(bytes.length);  
            console.log(ab)  
            let ia = new Uint8Array(ab);  
            for (let i = 0; i < bytes.length; i++) {  
                ia[i] = bytes.charCodeAt(i);  
            }  
            var blob = new Blob([ab], { type: 'application/octet-stream' });  
            var url = URL.createObjectURL(blob);  
            var a = document.createElement('a');  
            a.href = url;  
            a.download = new Date().valueOf() + ".jpg";  
            var e = document.createEvent('MouseEvents');  
            e.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);  
            a.dispatchEvent(e);  
            URL.revokeObjectURL(url);  
        },