base64转文件流

function toBlob(base64Data){
            let byteString;
            byteString = window.atob(base64Data.split(',')[1]);
            let ia = new Uint8Array(byteString.length);
            for(let i = 0; i < byteString.length; i++){
                ia[i] = byteString.charCodeAt(i);
            }
            return new Blob([ia],{type:'image/png'});
        }

 可用于base64转成文件流上传formdata