CODEWITHSUNDEEP
javascriptgoogle-chromegoogle-chrome-extension
Nandan Chitale
Nandan Chitale

Reputation: 31

Is it possible to get file type before downloading it through JavaScript?

I am trying to create a extension which will tell the user file type before downloading it via popup.Is there any method in JavaScript to analyse the file type before downloading it?

Upvotes: 1

Views: 643

Answers (1)

Karamell
Karamell

Reputation: 1032

You can get the file type by checking for the Content-type header when performing a HEAD request.

That won't download the content. For example, you can use XMLHttpRequest:

getMimeType = url => {
  const request = new XMLHttpRequest();
  request.open('HEAD', url);
  const promise = new Promise(resolve => {
    request.onreadystatechange = () => {
      if (request.readyState == request.DONE) {
        resolve(
          request
            .getAllResponseHeaders()
            .split('\n')
            .find(header => header.toLowerCase().startsWith('content-type'))
            .split(':')[1]
            .trim(),
        );
      }
    };
  });

  request.send();
  return promise;
};

// Random ad on this web site, prints image/jpeg
getMimeType('https://tpc.googlesyndication.com/simgad/18296964107941472197').then(console.log);

You might want to add error handling to the code as well

Upvotes: 1

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