Convert base64 string to File

base64-to-file.ts

function base64ToFile(base64: string, filename: string) {
  const [header, code] = base64.split(',')
  const cotnentType = header.replace(/(data:)|(;base64)/g, '');

  const byteStr = atob(code);
  const bytes = new Array(byteStr.length);
  for (var i = 0; i < byteStr.length; i++) {
      bytes[i] = byteStr.charCodeAt(i);
  }
  const byteArray = new Uint8Array(bytes);
  const blob = new Blob([byteArray], { type: cotnentType });

  return new File([blob], filename, { type: blob.type });
}

function fileToBase64(file: File) {
  return new Promise<string>((resolve, reject) => {
    var reader = new FileReader();
    reader.onload = function (e) {
      resolve(e.target.result as string);
    };
    reader.onerror = reject;
    reader.onabort = reject;
    reader.readAsDataURL(file);
  });  
  
}

async function main() {
  const base64 = `data:image/gif;base64,R0lGODlhCgAKAJEAAP////8AAAAA/wAAACH5BAAAAAAALAAAAAAKAAoAAAIWjC2Zhyoc3DOgAnXslfqo3mCMBJFMAQA7`
  const file = base64ToFile(base64, '00.png')
  console.log(file);
  console.log(await fileToBase64(file) === base64);
}

main().catch((err) => console.error(err));