base64转为图片

// base64 => image
const base642Img = async function(base64Str, dir) {
  // data:image/jpeg;base64,/asdasda

  const matches = base64Str.match(/^data:(.+?);base64,(.+)$/);
  try {
    const ext = matches[1].split("/")[1].replace("jpeg", "jpg");
    const file = path.join(dir, `${Date.now()}.${ext}`);

    await fs.writeFile(file, matches[2], "base64", err => {
      err ? console.log("write file error: ", err) : null;
    });
    console.log(file);
  } catch (ex) {
    console.log("非法 base64 字符串");
    console.log(ex);
  }
};