Type of event triggered by user file upload via INPUT element

I have a piece of code that reads the contents of a locally stored file. Here is what it looks like:

onFile(event: any) {
  console.log(event);
  const file = event.target.files[0];
  const reader = new FileReader();
  reader.onloadend = (ev: any) => { console.log(ev); };
  reader.readAsText(file);
}

After examining the console outputs, I noticed that the types being printed out are Event and ProgressEvent. So, I decided to adjust my methods to match the parameter types accordingly:

onFile(event: Event) {
  console.log(event);
  const file = event.target.files[0];
  const reader = new FileReader();
  reader.onloadend = (ev: ProgressEvent) => { console.log(ev, $event.target.result); };
  reader.readAsText(file);
}

Despite making these changes, TsLint still raises warnings about files[0] and result not being present in their types. Have I specified the incorrect type for the operations? What would be the appropriate type to use in this scenario?

Answer №1

It is important to note that target.files is a property specific to the input event's target. The compiler lacks knowledge about the type of event being passed, and there is no event type called input that can be provided as an object type. To address this, you have the option to either create your own event type or keep it as any. Check out more information at https://developer.mozilla.org/en-US/docs/Web/API/HTMLInputElement

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