How to know file type in file object when type propery is empty-CodePudding

I'm reading a file in android application with:

<ion-input type="file" (change)="readFile($event)"></ion-input>

I get a file object, and I can know the file type by checking the type property.

But some files have empty type property, as you can see in the following screenshot:

How can I konw the file type if it has empty type property and no extension?

CodePudding user response：

I had this problem a while ago, when using a Windows machine.
Fixed the issue following this answer.

To quote: "As i was expecting, issue is system specific where content-type for .csv type is missing under Registry (HKEY_CLASSES_ROOT.csv)."

CodePudding user response：

A solution that I find is to convert it to base64, for example with this code:

getBase64(file)
  {
    return new Promise((resolve, reject) =>
    {
      const reader = this.getFileReader();// this function is important for real devices. Without it the fielReader.onload will not be triggered in read device
      reader.readAsDataURL(file);
      reader.onload = () => resolve(reader.result);
      reader.onerror = error => reject(error);
    });
  }

the return will look like that:

'data:application/octet-stream;base64,T2dnUwACAAAAAAAAAAAAAAAAAAAAACqCBoIBE09wdXNIZWFkAQFoAIA AAAAAABPZ2dTAAAAAAAAAAA ...

As you can see, after data: we get the type. In this case application/octet-stream