Retrieve a file content as Base64 string

GetFileAsBase64.js

/**
 *
 * @param blob
 */
function getBase64(blob: Blob): Promise<string> {
    return new Promise<string>((resolve, reject) => {
        let reader = new FileReader();
        reader.onloadend = function() {
            let dataUrl = reader.result as string;
            let base64 = dataUrl.split(',')[1];
            resolve(base64);
        }
        reader.onerror = reject;
        reader.readAsDataURL(blob);
    });
}