Blob
A file-like object of immutable, raw data. Blobs represent data that isn't necessarily in a JavaScript-native format. The File interface is based on Blob, inheriting blob functionality and expanding it to support files on the user's system.
interface Blob {
readonly size: number;
readonly type: string;
arrayBuffer(): Promise<ArrayBuffer>;
stream(): ReadableStream<Uint8Array>;
text(): Promise<string>;
}var Blob: {
prototype: Blob;
new (blobParts?: BlobPart[], options?: BlobPropertyBag): Blob;
};