# @stackline/once full reference

`@stackline/once@1.0.0` is an independent, compatibility-first continuation
of `once@1.4.0`. It includes the signed upstream `v1.4.1` prototype-export fix
and retains the published ISC license line. It has zero runtime dependencies,
ES5 CommonJS source, ESM default-import interoperability, and TypeScript 3.9
and current declarations.

## API

- `once(callback)` returns a wrapper that invokes `callback` at most once,
  caches its result, preserves `this` and arguments, and exposes writable
  `.called` and `.value` state.
- `once.strict(callback)` returns the same public state but throws on every
  invocation after the first.
- `once.proto()` installs non-enumerable `.once()` and `.onceStrict()` methods
  on `Function.prototype`. This global mutation is retained for compatibility
  and remains opt-in; direct wrappers are preferred in libraries.

## Compatibility corrections

Reserved wrapper state (`called`, `value`, and `onceError`) cannot be replaced
by callback decorations. Other enumerable own decorations—including inherited
Object prototype names and an own `__proto__` property—are copied as ordinary
wrappy-compatible values. Wrapper state becomes sticky before the callback is
entered, including when the callback throws.

The declared runtime floor is Node.js 0.10.48. The implementation is ES5 and
the release gate parses that source as ES5, exercises the declared historical
runtime, and tests current Node.js, browser bundling, CommonJS, ESM default
interop, and TypeScript 3.9/current consumers.

## Install and migration

Scoped install: `npm install @stackline/once`

Historical-key alias: `npm install once@npm:@stackline/once`

Repository: https://github.com/alexandroit/stackline-once
Security policy: https://github.com/alexandroit/stackline-once/security/policy