FileReader readAsText() async issues?

Question

I have implemented the following code to parse a CSV via a selection:

export async function parse(file: File) {
           


        

Answer 1

To generalize @zero298's answer a tiny bit, here's the generic Promise-based wrapper around FileReader -

// get contents of a file as obtained from an html input type=file element
function getFileContents(file) {
  return new Promise((resolve, reject) => {
    let contents = ""
    const reader = new FileReader()
    reader.onloadend = function (e) {
      contents = e.target.result
      resolve(contents)
    }
    reader.onerror = function (e) {
      reject(e)
    }
    reader.readAsText(file)
  })
}

used like so -

async function parse(file) {
  const contents = await getFileContents(file)
  const result = contents.split(/\r\n|\n/)
  return result
}

or in the general case,

async function show(file) {
  const contents = await getFileContents(file)
  alert(contents)
}