• npm: https://www.npmjs.com/package/file-type

安装

npm i file-type

示例

const FileType = require('file-type');

(async () => {
  console.log(await FileType.fromFile('baidu.jp'));
  //=> {ext: 'png', mime: 'image/png'}
})();

参考
【实战】JavaScript 如何检测文件的类型？