Bun 入門ガイド

❯ Get-Content enum.ts
enum Level { Low, High }
console.log(Level.High)
❯ node enum.ts
...
SyntaxError [ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX]: TypeScript enum is not supported in strip-only mode

❯ bun --version
1.4.2

❯ bun init -y
 + .gitignore
 + index.ts
 + tsconfig.json (for editor autocomplete)
 + README.md

To get started, run:

    bun run index.ts

bun install v1.4.2 (744846f84)
Resolving dependencies
Resolved, downloaded and extracted [10]

+ @types/bun@1.4.2
+ typescript@7.0.2

6 packages installed [2.02s]
Saved lockfile
❯ Get-Content package.json
{
  "name": "hello",
  "module": "index.ts",
  "type": "module",
  "private": true,
  "devDependencies": {
    "@types/bun": "latest"
  },
  "peerDependencies": {
    "typescript": "^7"
  }
}

❯ Get-Content greet.ts
type User = { name: string; langs: string[] }

const user: User = { name: "Jam", langs: ["TypeScript", "Rust"] }
console.log(`${user.name} writes ${user.langs.join(" and ")}`)
console.log(`runtime: ${process.versions.bun ? "bun " + Bun.version : "node " + process.version}`)
❯ bun greet.ts
Jam writes TypeScript and Rust
runtime: bun 1.4.2

❯ node greet.ts
Jam writes TypeScript and Rust
runtime: node v26.11.1

❯ bun enum.ts
1

❯ bun run greet
$ bun greet.ts
Jam writes TypeScript and Rust
runtime: bun 1.4.2
❯ bun greet
$ bun greet.ts
Jam writes TypeScript and Rust
runtime: bun 1.4.2

❯ bun add zod
bun add v1.4.2 (744846f84)
Resolving dependencies
Resolved, downloaded and extracted [2]

installed zod@4.6.5

1 package installed [916.00ms]
Saved lockfile
❯ bun add -d @biomejs/biome
bun add v1.4.2 (744846f84)
Resolving dependencies
Resolved, downloaded and extracted [18]

installed @biomejs/biome@2.5.15 with binaries:
 - biome

2 packages installed [538.00ms]
Saved lockfile

❯ Get-Content package.json
{
  "name": "hello",
  "module": "index.ts",
  "type": "module",
  "private": true,
  "devDependencies": {
    "@biomejs/biome": "^2.5.15",
    "@types/bun": "latest"
  },
  "peerDependencies": {
    "typescript": "^7"
  },
  "dependencies": {
    "zod": "^4.6.5"
  }
}

❯ bun pm ls
C:\Users\Jam\bun-demo\hello node_modules (35 installed)
├── @biomejs/biome@2.5.15
├── @types/bun@1.4.2
├── typescript@7.0.2
└── zod@4.6.5

❯ Get-Content bun.lock -TotalCount 22
{
  "lockfileVersion": 2,
  "configVersion": 1,
  "workspaces": {
    "": {
      "name": "hello",
      "dependencies": {
        "zod": "^4.6.5",
      },
      "devDependencies": {
        "@biomejs/biome": "^2.5.15",
        "@types/bun": "latest",
      },
      "peerDependencies": {
        "typescript": "^7",
      },
    },
  },
  "packages": {
    "@biomejs/biome": ["@biomejs/biome@2.5.15", "", { "optionalDependencies": { "@biomejs/cli-darwin-arm64": "2.5.15", ... } }, "sha512-WZTW4slm/..."],

❯ bun remove zod
bun remove v1.4.2 (744846f84)

- zod
1 package removed [38.00ms]
Saved lockfile

❯ bunx cowsay hello from bunx
Resolving dependencies
Resolved, downloaded and extracted [100]
Saved lockfile
 _________________
< hello from bunx >
 -----------------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

❯ bunx biome --version
Version: 2.5.15

❯ bun add core-js
bun add v1.4.2 (744846f84)
Resolving dependencies
Resolved, downloaded and extracted [4]

installed core-js@3.50.0

1 package installed [25.54s]

Blocked 1 postinstall. Run `bun pm untrusted` for details.
Saved lockfile
❯ bun pm untrusted
bun pm untrusted v1.4.2 (744846f84)

.\node_modules\core-js @3.50.0
 » [postinstall]: node -e "try{require('./postinstall')}catch(e){}"

These dependencies had their lifecycle scripts blocked during install.

If you trust them and wish to run their scripts, use `bun pm trust`.

❯ bun pm trust core-js
bun pm trust v1.4.2 (744846f84)

.\node_modules\core-js @3.50.0
 ✓ [postinstall]: node -e "try{require('./postinstall')}catch(e){}"

 1 script ran across 1 package [407.00ms]
❯ Select-String trustedDependencies -Context 0,2 package.json

> package.json:21:  "trustedDependencies": [
  package.json:22:    "core-js"
  package.json:23:  ]

❯ Get-Content slugify.ts
export function slugify(title: string): string {
  return title.toLowerCase().trim().replace(/\s+/g, "-")
}
❯ Get-Content slugify.test.ts
import { describe, expect, test } from "bun:test"
import { slugify } from "./slugify"

describe("slugify", () => {
  test("joins words with hyphens", () => {
    expect(slugify("Getting Started with Bun")).toBe("getting-started-with-bun")
  })

  test("drops punctuation", () => {
    expect(slugify("Hello, Bun!")).toBe("hello-bun")
  })
})
❯ bun test
bun test v1.4.2 (744846f84)

slugify.test.ts:
 5 |   test("joins words with hyphens", () => {
 6 |     expect(slugify("Getting Started with Bun")).toBe("getting-started-with-bun")
 7 |   })
 8 |
 9 |   test("drops punctuation", () => {
10 |     expect(slugify("Hello, Bun!")).toBe("hello-bun")
                                        ^
error: expect(received).toBe(expected)

Expected: "hello-bun"
Received: "hello,-bun!"

      at <anonymous> (C:\Users\Jam\bun-demo\hello\slugify.test.ts:10:36)
(fail) slugify > drops punctuation [0.99ms]

 1 pass
 1 fail
 2 expect() calls
Ran 2 tests across 1 file. [24.00ms]

❯ Get-Content slugify.ts
export function slugify(title: string): string {
  return title
    .toLowerCase()
    .replace(/[^\p{L}\p{N}\s-]/gu, "")
    .trim()
    .replace(/\s+/g, "-")
}
❯ bun test
bun test v1.4.2 (744846f84)

 2 pass
 0 fail
 2 expect() calls
Ran 2 tests across 1 file. [16.00ms]

❯ Get-Content bunfig.toml
[test]
root = "./test/unit"
randomize = true
preload = ["./test/unit/happydom.ts", "./test/unit/setup-next-navigation-mock.ts"]

❯ bun test:unit
...
 --seed=1780192552
 841 pass
 0 fail
 39881 expect() calls
Ran 841 tests across 108 files. [68.96s]

❯ ls
node_modules
date.test.js
package-lock.json
package.json
❯ bun install
bun install v1.4.2 (744846f84)

Checked 2 installs across 3 packages (no changes) [120.00ms]
[1.69ms] migrated lockfile from package-lock.json
Saved lockfile
❯ ls
node_modules
bun.lock
date.test.js
package-lock.json
package.json

❯ Get-Content date.test.js
const dayjs = require("dayjs")

test("adds a day", () => {
  expect(dayjs("2026-10-08").add(1, "day").format("YYYY-MM-DD")).toBe("2026-10-09")
})
❯ bun test
bun test v1.4.2 (744846f84)

 1 pass
 0 fail
 1 expect() calls
Ran 1 test across 1 file. [214.00ms]

❯ Get-Content who.js
console.log(process.versions.bun ? `bun ${process.versions.bun}` : `node ${process.version}`)
❯ Get-Content package.json
{ "name": "who", "scripts": { "who": "node who.js" } }

❯ (Get-Command node).Source
C:\Users\Jam\AppData\Local\mise\installs\node\26.11.1\node.exe
❯ bun run who
$ node who.js
node v26.11.1
❯ bun run --bun who
$ node who.js
bun 1.4.2

❯ Get-Command node
Get-Command: 用語 'node' は、コマンドレット、関数、スクリプト ファイル、または実行可能プログラムの名前として認識されません。
名前のスペルを確認するか、パスが含まれている場合はパスが正しいことを確認してから、もう一度お試しください。
❯ bun run who
$ node who.js
bun 1.4.2
❯ bun run where
$ where node
C:\Users\Jam\AppData\Local\Temp\bun-node-744846f84\node.exe

❯ Get-CimInstance Win32_Process | Where-Object { $_.Name -eq "bun.exe" -or $_.CommandLine -match "\\next" } | Select-Object ProcessId, ParentProcessId, ExecutablePath

ProcessId ParentProcessId ExecutablePath
--------- --------------- --------------
    18864           11352 C:\Users\Jam\AppData\Local\mise\installs\bun\1.4.2\bin\bun.exe
     7292           18864 C:\Users\Jam\Documents\blog\node_modules\.bin\next.exe
     6924            7292 C:\Users\Jam\AppData\Local\mise\installs\node\26.11.1\node.exe
    21972            6924 C:\Users\Jam\AppData\Local\mise\installs\node\26.11.1\node.exe

❯ wslc run --rm oven/bun:1.4.2 which node
/usr/local/bun-node-fallback-bin/node
❯ wslc run --rm oven/bun:1.4.2 readlink -f /usr/local/bun-node-fallback-bin/node
/usr/local/bin/bun
❯ wslc run --rm oven/bun:1.4.2 node -p process.versions.bun
1.4.2
❯ wslc run --rm oven/bun:1.4.2 node -p process.version
v26.3.0

❯ deno --version
deno 2.9.7 (stable, release, x86_64-pc-windows-msvc)
v8 15.0.245.2-rusty
typescript 6.0.3
❯ deno enum.ts
1

❯ Get-Content latest.ts
const res = await fetch("https://registry.npmjs.org/bun/latest")
console.log((await res.json()).version)
❯ deno latest.ts
error: Uncaught (in promise) NotCapable: Requires net access to "registry.npmjs.org:443", run again with the --allow-net flag
...
❯ deno --allow-net=registry.npmjs.org latest.ts
1.4.2
❯ bun latest.ts
1.4.2

❯ pnpm install
...
dependencies:
+ core-js 3.50.0

Error: ERR_PNPM_IGNORED_BUILDS

  × installing dependencies
  ╰─▶ Ignored build scripts: core-js@3.50.0
  help: Run "pnpm approve-builds" to pick which dependencies should be allowed
        to run scripts.

❯ deno install
...
Dependencies:
+ npm:core-js 3.50.0

╭ Warning
│
│  Ignored build scripts for packages:
│  npm:core-js@3.50.0
│
│  Run "deno approve-scripts" to run build scripts.
╰─

❯ npm install --foreground-scripts

> core-js@3.50.0 postinstall
> node -e "try{require('./postinstall')}catch(e){}"

Thank you for using core-js ( https://github.com/zloirock/core-js ) for polyfilling JavaScript standard library!
...
added 1 package, and audited 2 packages in 37s
...
npm warn install-scripts 1 package has install scripts not yet covered by allowScripts:
npm warn install-scripts   core-js@3.50.0 (postinstall: node -e "try{require('./postinstall')}catch(e){}")
npm warn install-scripts
npm warn install-scripts Run `npm install-scripts ls` to review, or `npm install-scripts approve <pkg>` to allow.

❯ Get-Content package.json
{ "name": "who", "scripts": { "test": "echo this is the test script" } }
❯ bun run test
$ echo this is the test script
this is the test script
❯ bun test
bun test v1.4.2 (744846f84)
error: 0 test files matching **{.test,.spec,_test_,_spec_}.{js,ts,jsx,tsx} in --cwd="C:\Users\Jam\bun-demo\who"

❯ bun add esbuild
bun add v1.4.2 (744846f84)
Resolving dependencies
Resolved, downloaded and extracted [54]

installed esbuild@0.28.2 with binaries:
 - esbuild

2 packages installed [1032.00ms]

Blocked 1 postinstall. Run `bun pm untrusted` for details.
Saved lockfile
❯ bun pm untrusted
bun pm untrusted v1.4.2 (744846f84)

.\node_modules\esbuild @0.28.2
 » [postinstall]: node install.js

These dependencies had their lifecycle scripts blocked during install.

If you trust them and wish to run their scripts, use `bun pm trust`.

❯ bunx esbuild --version
0.28.2