bun-repl

bun-repl

Experimental unofficial REPL for Bun

Powered by Bun itself with the help of swc and JSC's ShadowRealm API

Install

bun add -g bun-repl

⚠️ Due to workarounds for Bun-specific issues, installation on other package managers like npm or yarn will not work.

Usage

bun run repl
# or
bun-repl

Type .help within the REPL for a list of commands.

Press ↑+Enter to travel up the execution history.

Press ↓+Enter to travel back down.

Features

• Seamless JavaScript & TypeScript execution
• Top level import syntax supported (import fs from 'fs')
• Import either CommonJS or ESM local files and packages into the REPL
• Node.js REPL special underscore variables provided (_ and _error)
• Execution history (↑ ↓)
• REPL Commands (.command)

Known issues & limitations

Please keep in mind this is unofficial and experimental software built on top of experimental software, there ARE bugs. Additionally, Bun will obviously be getting an official native REPL in the future which certainly will be much better, this module is merely serving as a temporary alternative until then.

• Top level await is not supported.
  • Reason: Usage of eval()
• Multi-line inputs are not supported.
  • Reason: Same as below.
• Pressing ← and → to traverse the input with the cursor is not supported.
  • Reason: Same as below.
• The execution history is buggy to navigate and doesn't support backspacing past the history entry.
  • Reason: Bun's current lack of support for event-based streams limits us to prompt(), which provides little to no control over the input as its being written. This also makes it impossible to intercept keypresses/combinations.
• There is a space between the execution history entry and your appended code.
  • Reason: prompt() automatically inserts a space at the end, with no way to turn it off. Yes, quite annoying.
• To preserve lexically-scoped variables (let & const) across REPL runs, they need to be converted to var, which disrupts their behavior, especially const's
  • Reason: Usage of eval() which has its own lexical scope.
• Some modules fail to resolve their imports within the REPL, such as fs/promises.
  • Reason: Unknown...