Using FileReader to convert a file

convertToBase64.js

/**
 * convertToBase64
 * @param binaryData: Input data from an <input type="file">
 */
function convertToBase64(binaryData) {
    // use a FileReader
    // https://developer.mozilla.org/en-US/docs/Web/API/FileReader
    var reader = new FileReader();
    reader.onload = function (event) {
        // try to read whatever file has been 'readAsDataURL'
        try {
            // event target result is our base64 encoded type
            // this is whatever file has been reader during 'readAsDataURL'
            console.log(event.target.result);
            return(event.target.result);
        // catch an error if one occurs...
        } catch (ex) {
            // output a warning in the DevTools console
            throw new Error("Couldn't convert file: " + ex);
        }
    }
    // read the file argument
    reader.readAsDataURL(binaryData);
};