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Convert a Uint8Array

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Uint8Array is the workhorse binary type in Deno: file reads, network payloads, and hashes all produce or consume it. This example shows how to convert one into the other common binary and text representations.

We start with a Uint8Array containing the bytes of the string "Hello".
const bytes = new TextEncoder().encode("Hello");
To convert to a string, decode the bytes with TextDecoder.
const text = new TextDecoder().decode(bytes);
console.log(text); // Hello
A Uint8Array is a view over an underlying ArrayBuffer. The view may cover only part of that buffer, so to get an exact ArrayBuffer, slice the range described by byteOffset and byteLength.
const exact = bytes.buffer.slice(
  bytes.byteOffset,
  bytes.byteOffset + bytes.byteLength,
);
console.log(exact.byteLength); // 5
If the view is known to span its whole buffer, the buffer property can be used directly. This does not copy the bytes.
console.log(bytes.buffer.byteLength); // 5
To convert to a Blob, pass the array in the parts list of the Blob constructor.
const blob = new Blob([bytes]);
console.log(blob.size); // 5
To create a DataView over the same bytes, pass the buffer together with the offset and length of the view.
const view = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength);
console.log(view.getUint8(4)); // 111
ReadableStream.from wraps any iterable into a stream. This is useful for APIs that consume streams, like the Response constructor.
const stream = ReadableStream.from([bytes]);
console.log(stream instanceof ReadableStream); // true
To convert to a base64 or hex string, use the built-in methods available since Deno 2.x. The matching fromBase64 and fromHex methods decode back.
console.log(bytes.toBase64()); // SGVsbG8=
console.log(bytes.toHex()); // 48656c6c6f
const decoded = Uint8Array.fromBase64("SGVsbG8=");
console.log(decoded); // Uint8Array(5) [ 72, 101, 108, 108, 111 ]
When working with Node.js APIs, convert to a Buffer with Buffer.from. This copies the bytes. To share memory instead, pass the underlying buffer together with the offset and length.
import { Buffer } from "node:buffer";
const nodeBuffer = Buffer.from(bytes);
console.log(nodeBuffer.toString("utf8")); // Hello

Run this example locally using the Deno CLI:

deno run https://docs.deno.com/examples/scripts/convert_uint8array.ts

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