CODE EXAMPLE FOR JAVASCRIPT

javascript change IFormFile to base64string

// Be aware! We are handling only the first <input type="file" /> element
// To avoid errors, it should be placed before this piece of code
var input = document.querySelector('input[type=file]');

// You will receive the Base64 value every time a user selects a file from his device
// As an example I selected a one-pixel red dot GIF file from my computer
input.onchange = function () {
  var file = input.files[0],
    reader = new FileReader();

  reader.onloadend = function () {
    // Since it contains the Data URI, we should remove the prefix and keep only Base64 string
    var b64 = reader.result.replace(/^data:.+;base64,/, '');
    console.log(b64); //-> "R0lGODdhAQABAPAAAP8AAAAAACwAAAAAAQABAAACAkQBADs="
  };

  reader.readAsDataURL(file);
};