Converter link de uma imagem para base64

convert_img_to_base64.js

function toDataUrl(url, callback) {
    var xhr = new XMLHttpRequest();
    xhr.onload = function() {
        var reader = new FileReader();
        reader.onloadend = function() {
            callback(reader.result);
        }
        reader.readAsDataURL(xhr.response);
    };
    xhr.open('GET', url);
    xhr.responseType = 'blob';
    xhr.send();
}

toDataUrl("https://s3-us-east-2.amazonaws.com/minhaigreja-production/images/articles/5/original/joao_capitulo_7_versiculo_53.jpg?1519132286", function(myBase64) {
    console.log(myBase64); // myBase64 is the base64 string
});