Error using async and await with filereader

I'm trying to read a file using FileReader:

async readFile(event: any) {
    var file = event.target.files[0];
    var data:string
    if (file) {   
        var reader:FileReader = new FileReader();
         reader.onload = async function (evt : FileReaderEvent) {
            data = await evt.target.result;
            console.log(evt.target.result);

        };
        console.log(file);
        console.log(data);
        await reader.readAsText(file);
        await this.processFileContent(data);
    }
 }

However, evt.target.result still gets printed after my console.log(file) call.

Does anyone know how I can obtain the result of the file and pass it to my processFileContent function?

Use the new read methods on the blob itself

/** @type {Event} evt */
async readFile (evt) {
  const [file] = evt.target.files
  if (!file) return
  const data = await file.text()
  return this.processFileContent(data)
}

Alternative:

evt.target.files[0]?.text().then(this.processFileContent)

Needed to leverage reader to convert blob to base64, prefer to use async-await syntax so I chose to extract reader logic into helper like this:

//* Convert resBlob to base64
export const blobToData = (blob: Blob) => {
  return new Promise((resolve) => {
    const reader = new FileReader()
    reader.onloadend = () => resolve(reader.result)
    reader.readAsDataURL(blob)
  })
}

and calling it using await in main code:

//* Convert resBlob to dataUrl and resolve
const resData = await blobToData(resBlob)