Convert HTML file input to binary string

convertFileUploadToBinary.js

// The below function accepts the HTMLInputElement event from a <input type="file" />
// and returns a binary string
function readFileDataAsBase64(e) {
    const file = e.target.files[0];

    return new Promise((resolve, reject) => {
      const reader = new FileReader();

      reader.onload = (event) => {
        resolve(event.target.result);
      };

      reader.onerror = (err) => {
        reject(err);
      };

      reader.readAsBinaryString(file);
    });
  }