blob

The Blob class represents immutable raw binary data. Blobs are commonly used for file-like objects, uploads, and binary manipulation.

API Surface

Class: Blob

  • new Blob(sources[, options]) — create blob from array of parts.
    • Parts: strings, BufferSource, Blob.
    • Options: { type: "mime/type" }.

Properties

  • blob.size — size in bytes.
  • blob.type — MIME type string.

Methods

  • blob.slice([start], [end], [type]) — return a new Blob view.
  • blob.arrayBuffer() — resolve to ArrayBuffer.
  • blob.text() — resolve to string.
  • blob.stream() — readable stream of blob data.

Examples (English only)

// Create a blob from text
const b = new Blob(["Hello Bnlang"], { type: "text/plain" });
console.log("size:", b.size, "type:", b.type);

// Convert to text
const txt = await b.text();
console.log("text:", txt);

// Slice & arrayBuffer
const part = b.slice(0, 5, "text/plain");
console.log("part text:", await part.text());

// Stream blob
for await (const chunk of b.stream()) {
  console.log("chunk:", chunk);
}

Notes

  • Blobs are immutable; operations return new Blobs.
  • MIME type is advisory; consumers may ignore it.
  • Use Blob with FormData for file uploads.
  • For random access binary edits, use Buffer instead.