Read a file synchronously in Javascript

Question

I would like to read a file and convert it into a base64 encoded string using the FileReader object. Here\'s the code I use :

    var reader = new FileReader();
         


        

Answer 1

The below code works sync way to read the file and return its content as text (string)

 function SyncFileReader(file) {
    let self = this;
    let ready = false;
    let result = '';

    const sleep = function (ms) {
      return new Promise(resolve => setTimeout(resolve, ms));
    }

    self.readAsDataURL = async function() {
        while (ready === false) {
          await sleep(100);
        }
        return result;
    }    

    const reader = new FileReader();
    reader.onloadend = function(evt) {
        result = evt.target.result;
        ready = true;
    };
    reader.readAsDataURL(file);
  }

Usage :

const fileReader = new SyncFileReader(file);
const arrayBuffer = await fileReader.readAsDataURL();