Introduction to Effect Platform

@effect/platform is a library for building platform-independent abstractions in environments such as Node.js, Bun, and browsers.

With @effect/platform, you can integrate abstract services like Terminal, FileSystem or Path into your program. When assembling your final application, you can provide specific layers for the target platform using the corresponding packages:

@effect/platform-node for Node.js
@effect/platform-bun for Bun
@effect/platform-browser for browsers

Installation

To install the beta version:

npm install @effect/platform

pnpm add @effect/platform

yarn add @effect/platform

bun add @effect/platform

Getting Started with Cross-Platform Programming

Here’s a basic example using the Path module to create a file path, which can run across different environments:

Example (Cross-Platform Path Handling)

1
import { import Path
Path } from "@effect/platform"
2
import { import Effect
Effect } from "effect"
3

4
const const program: Effect.Effect<void, never, Path.Path>
program = import Effect
Effect.const gen: <YieldWrap<Tag<Path.Path, Path.Path>>, void>(f: (resume: Effect.Adapter) => Generator<YieldWrap<Tag<Path.Path, Path.Path>>, void, never>) => Effect.Effect<...> (+1 overload)
gen(function* () {
5
  // Access the Path service
6
  const const path: Path.Path
path = yield* import Path
Path.namespace Path
const Path: Tag<Path.Path, Path.Path>
Path
7

8
  // Join parts of a path to create a complete file path
9
  const const mypath: string
mypath = const path: Path.Path
path.(property) Path.join: (...paths: ReadonlyArray<string>) => string
join("tmp", "file.txt")
10

11
  namespace console
var console: ConsoleThe `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
console.(method) Console.log(message?: any, ...optionalParams: any[]): voidPrints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
log(const mypath: string
mypath)
12
})

Running the Program in Node.js

First, install the Node.js-specific package:

npm install @effect/platform-node

pnpm add @effect/platform-node

yarn add @effect/platform-node

Update the program to load the Node.js-specific context:

Example (Providing Node.js Context)

1
import { import Path
Path } from "@effect/platform"
2
import { import Effect
Effect } from "effect"
3
import { import NodeContext
NodeContext, import NodeRuntime
NodeRuntime } from "@effect/platform-node"
4

5
const const program: Effect.Effect<void, never, Path.Path>
program = import Effect
Effect.const gen: <YieldWrap<Tag<Path.Path, Path.Path>>, void>(f: (resume: Effect.Adapter) => Generator<YieldWrap<Tag<Path.Path, Path.Path>>, void, never>) => Effect.Effect<...> (+1 overload)
gen(function* () {
6
  // Access the Path service
7
  const const path: Path.Path
path = yield* import Path
Path.namespace Path
const Path: Tag<Path.Path, Path.Path>
Path
8

9
  // Join parts of a path to create a complete file path
10
  const const mypath: string
mypath = const path: Path.Path
path.(property) Path.join: (...paths: ReadonlyArray<string>) => string
join("tmp", "file.txt")
11

12
  namespace console
var console: ConsoleThe `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
console.(method) Console.log(message?: any, ...optionalParams: any[]): voidPrints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
log(const mypath: string
mypath)
13
})
14

15
import NodeRuntime
NodeRuntime.const runMain: RunMain
<never, void>(effect: Effect.Effect<void, never, never>, options?: {
    readonly disableErrorReporting?: boolean | undefined;
    readonly disablePrettyLogger?: boolean | undefined;
    readonly teardown?: Teardown | undefined;
}) => void (+1 overload)
runMain(const program: Effect.Effect<void, never, Path.Path>
program.(method) Pipeable.pipe<Effect.Effect<void, never, Path.Path>, Effect.Effect<void, never, never>>(this: Effect.Effect<...>, ab: (_: Effect.Effect<void, never, Path.Path>) => Effect.Effect<void, never, never>): Effect.Effect<...> (+21 overloads)
pipe(import Effect
Effect.const provide: <NodeContext.NodeContext, never, never>(layer: Layer<NodeContext.NodeContext, never, never>) => <A, E, R>(self: Effect.Effect<A, E, R>) => Effect.Effect<...> (+9 overloads)Splits the context into two parts, providing one part using the
specified layer/context/runtime and leaving the remainder `R0`
provide(import NodeContext
NodeContext.const layer: Layer<NodeContext.NodeContext, never, never>
layer)))

Finally, run the program in Node.js using tsx:

npx tsx index.ts

pnpm dlx tsx index.ts

yarn dlx tsx index.ts

Running the Program in Bun

To run the same program in Bun, first install the Bun-specific package:

bun add @effect/platform-bun

Update the program to use the Bun-specific context:

Example (Providing Bun Context)

1
import { import Path
Path } from "@effect/platform"
2
import { import Effect
Effect } from "effect"
3
import { import BunContext
BunContext, import BunRuntime
BunRuntime } from "@effect/platform-bun"
4

5
const const program: Effect.Effect<void, never, Path.Path>
program = import Effect
Effect.const gen: <YieldWrap<Tag<Path.Path, Path.Path>>, void>(f: (resume: Effect.Adapter) => Generator<YieldWrap<Tag<Path.Path, Path.Path>>, void, never>) => Effect.Effect<...> (+1 overload)
gen(function* () {
6
  // Access the Path service
7
  const const path: Path.Path
path = yield* import Path
Path.namespace Path
const Path: Tag<Path.Path, Path.Path>
Path
8

9
  // Join parts of a path to create a complete file path
10
  const const mypath: string
mypath = const path: Path.Path
path.(property) Path.join: (...paths: ReadonlyArray<string>) => string
join("tmp", "file.txt")
11

12
  namespace console
var console: ConsoleThe `console` module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.

The module exports two specific components:

* A `Console` class with methods such as `console.log()`, `console.error()` and `console.warn()` that can be used to write to any Node.js stream.
* A global `console` instance configured to write to [`process.stdout`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstdout) and
[`process.stderr`](https://nodejs.org/docs/latest-v22.x/api/process.html#processstderr). The global `console` can be used without importing the `node:console` module.

_**Warning**_: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the [`note on process I/O`](https://nodejs.org/docs/latest-v22.x/api/process.html#a-note-on-process-io) for
more information.

Example using the global `console`:

```js
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
```

Example using the `Console` class:

```js
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
```
console.(method) Console.log(message?: any, ...optionalParams: any[]): voidPrints to `stdout` with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to [`printf(3)`](http://man7.org/linux/man-pages/man3/printf.3.html)
(the arguments are all passed to [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args)).

```js
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
```

See [`util.format()`](https://nodejs.org/docs/latest-v22.x/api/util.html#utilformatformat-args) for more information.
log(const mypath: string
mypath)
13
})
14

15
import BunRuntime
BunRuntime.const runMain: RunMain
<never, void>(effect: Effect.Effect<void, never, never>, options?: {
    readonly disableErrorReporting?: boolean | undefined;
    readonly disablePrettyLogger?: boolean | undefined;
    readonly teardown?: Teardown | undefined;
}) => void (+1 overload)
runMain(const program: Effect.Effect<void, never, Path.Path>
program.(method) Pipeable.pipe<Effect.Effect<void, never, Path.Path>, Effect.Effect<void, never, never>>(this: Effect.Effect<...>, ab: (_: Effect.Effect<void, never, Path.Path>) => Effect.Effect<void, never, never>): Effect.Effect<...> (+21 overloads)
pipe(import Effect
Effect.const provide: <BunContext.BunContext, never, never>(layer: Layer<BunContext.BunContext, never, never>) => <A, E, R>(self: Effect.Effect<A, E, R>) => Effect.Effect<...> (+9 overloads)Splits the context into two parts, providing one part using the
specified layer/context/runtime and leaving the remainder `R0`
provide(import BunContext
BunContext.const layer: Layer<BunContext.BunContext, never, never>
layer)))

Run the program in Bun:

bun index.ts
tmp/file.txt