# @yume-chan/no-data-view

> Plain methods to avoid creating `DataView`s

Latest version **2.0.0** (published 2025-04-04) · MIT license · 0 weekly downloads

## Install

```sh
npm install @yume-chan/no-data-view
pnpm add @yume-chan/no-data-view
yarn add @yume-chan/no-data-view
bun add @yume-chan/no-data-view
```

## Health

**Score 60/100 (C)** — status: stable.

Positive: has types; esm support; no vulnerabilities; has provenance; high maintenance score; high quality score.

Warnings: low downloads.

Negative: stale.

## Facts

| | |
|---|---|
| Version | 2.0.0 |
| Published | 2025-04-04 |
| First published | 2024-06-18 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 0 |
| Unpacked size | 79.5 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| Provenance | attested (GitHub Actions) |
| GitHub stars | 3249 |
| Author | Simon Chan |
| Maintainers | yume-chan |

## Links

- npm: https://www.npmjs.com/package/@yume-chan/no-data-view
- Repository: https://github.com/yume-chan/ya-webadb
- Homepage: https://github.com/yume-chan/ya-webadb/tree/main/packages/no-data-view#readme
- Issues: https://github.com/yume-chan/ya-webadb/issues
- npm.io page: https://npm.io/package/@yume-chan/no-data-view

## Recent versions

- 2.0.0 (latest) — 2025-04-04
- 3.0.0-beta.4 (beta) — 2026-10-09
- 3.0.0-beta.3 — 2026-09-17
- 3.0.0-beta.2 — 2026-08-11
- 3.0.0-beta.1 — 2026-08-01
- 3.0.0-beta.0 — 2026-07-28
- 1.0.0 — 2024-12-02
- 0.0.0-next-20241130050937 — 2024-11-30
- 0.0.0-next-20241129144018 — 2024-11-29
- 0.0.0-next-20240917062356 — 2024-09-17
- 0.0.0-20240714132542 — 2024-07-14
- 0.0.24 — 2024-06-18

## README

# @yume-chan/no-data-view

Plain methods to avoid creating `DataView`s.

## Why?

If you have many short `Uint8Array`s and you want to read numbers from them, creating `DataView`s for each of them is not a good idea:

Each `DataView` needs to allocate some memory, it impacts the performance, increases the memory usage, and adds GC pressure.

(If you are using `DataView`s for large `ArrayBuffer`s, it's fine)

## How does it work?

This package provides a set of methods to read/write numbers from `Uint8Array`s without creating `DataView`s.

Because they are very basic number operations, the performance between a JavaScript implementation and the native `DataView` is nearly identical.

(Except for `getBigUint64` and `setBigUint64`, Chrome uses an inefficient implementation, so this JavaScript implementation is even faster than the native one).

Check the [benchmark](./benchmark.md) for more details.

## Why there is no `setInt8`?

Assign a negative number to a `Uint8Array` will treat it as an unsigned number, so there is no need to provide a `setInt8` method.

(Assigning a number to `Uint8Array` directly translates to byte storing CPU instruction so it's very fast)

In fact, `setIntXX` and `setUintXX` is the same method, they are both provided only for consistency.

```ts
import { getInt8 } from "@yume-chan/no-data-view";

const array = new Uint8Array(1);
array[0] = -1;
console.log(array[0]); // 255
console.log(new Int8Array(array.buffer)[0]); // -1
console.log(getInt8(array, 0)); // -1
```

## Why `setIntXX` doesn't need `& 0xFF`?

Similarly, `Uint8Array` only stores the lowest 8 bits of a number, so there is no need to mask the number.

```ts
const array = new Uint8Array(2);
array[0] = 0x1234;
console.log(array[0]); // 52 (0x34)
console.log(array[1]); // 0
```

## But why `setBigUint64` have `& 0xFFn`?

Because `BigInt` can contain a super huge value, that even when shifted to the right, is still not representable by `Number`. So they must be masked with `0xFFn` before converting to `Number`.

(Converting between `BigInt` and `Number` has very little performance impact, because they only need one number extension or truncation CPU instruction)

```ts
const value = (BigInt(Number.MAX_SAFE_INTEGER) + 2n) << 8n;
console.log((value >> 8n) & 0xffn); // 1n
console.log(Number(value >> 8n) & 0xff); // 0
```

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_Source: https://npm.io/package/@yume-chan/no-data-view · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._