this._realReader.readAsArrayBuffer is not a function. (In 'this._realReader.readAsArrayBuffer(file)', 'this._realReader.readAsArrayBuffer' is undefined)

FileReader.prototype.readAsArrayBuffer = function (file) { if (initRead(this, file)) { return this._realReader.readAsArrayBuffer(file); } const totalSize = file.end - file.start; readSuccessCallback.bind(this)('readAsArrayBuffer', null, file.start, totalSize, function (r) { const resultArray = (this._progress === 0 ? new Uint8Array(totalSize) : new Uint8Array(this._result)); resultArray.set(new Uint8Array(r), this._progress); this._result = resultArray.buffer; }.bind(this)); }; 

writeBlobToFile = (file: FileEntry, blob): angular.IPromise<void> => { return this.$q((resolve, reject) => { file.createWriter((fileWriter) => { fileWriter.write(blob); fileWriter.onwriteend = resolve; fileWriter.onerror = reject; }, reject); }); };