if (typeof String.prototype.startsWith != 'function') {
    String.prototype.startsWith = function (str) {
        return this.slice(0, str.length) == str
    }
}

function dataURItoBlob(dataURI) {
    // convert base64 to raw binary data held in a string
    // doesn't handle URLEncoded DataURIs - see SO answer #6850276 for code that does this
    var byteString = atob(dataURI.split(',')[1]);

    // separate out the mime component
    var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0]

    // write the bytes of the string to an ArrayBuffer
    var ab = new ArrayBuffer(byteString.length);
    var ia = new Uint8Array(ab);
    for (var i = 0; i < byteString.length; i++) {
        ia[i] = byteString.charCodeAt(i);
    }

    // write the ArrayBuffer to a blob, and you're done
    return new Blob([ab], { type: mimeString });
}

function isiframed() {
    try {
        return window.self !== window.top;
    } catch (e) {
        return true;
    }
}