deno repl, interactive scripting promptdeno repl [OPTIONS] [-- [ARGS]...]Starts a read-eval-print-loop, which lets you interactively build up program state in the global context. It is especially useful for quick prototyping and checking snippets of code.
TypeScript is supported, however it is not type-checked, only transpiled.
--cert Load certificate authority from PEM encoded file.
--conditions Use this argument to specify custom conditions for npm package exports. You can also use DENO_CONDITIONS env var. .
--config Short flag: -c
Configure different aspects of deno including TypeScript, linting, and code formatting. Typically the configuration file will be called deno.json or deno.jsonc and automatically detected; in that case this flag is not necessary.
--env-file Load environment variables from local file Only the first environment variable with a given key is used. Existing process environment variables are not overwritten, so if variables with the same names already exist in the environment, their values will be preserved. Where multiple declarations for the same environment variable exist in your .env file, the first one encountered is applied. This is determined by the order of the files you pass as arguments.
--eval Evaluates the provided code when the REPL starts.
--eval-file Evaluates the provided file(s) as scripts when the REPL starts. Accepts file paths and URLs.
--location Value of globalThis.location used by some web APIs.
--no-config Disable automatic loading of the configuration file.
--preload A list of files that will be executed before the main module.
--seed Set the random number generator seed.
--v8-flags To see a list of all available flags use --v8-flags=--help Flags can also be set via the DENO_V8_FLAGS environment variable. Any flags set with this flag are appended after the DENO_V8_FLAGS environment variable.
--cached-only Require that remote dependencies are already cached.
--frozen Error out if lockfile is out of date.
--import-map Load import map file from local file or remote URL.
--lock Check the specified lock file. (If value is not provided, defaults to "./deno.lock").
--no-lock Disable auto discovery of the lock file.
--no-npm Do not resolve npm modules.
--no-remote Do not resolve remote modules.
--node-modules-dir Sets the node modules management mode for npm packages.
--reload Short flag: -r
Reload source code cache (recompile TypeScript) no value Reload everything jsr:@std/http/file-server,jsr:@std/assert/assert-equals Reloads specific modules npm: Reload all npm modules npm:chalk Reload specific npm module.
--vendor Toggles local vendor folder usage for remote modules and a node_modules folder for npm packages.
--inspect Activate inspector on host:port [default: 127.0.0.1:9229]
--inspect-brk Activate inspector on host:port, wait for debugger to connect and break at the start of user script.
--inspect-wait Activate inspector on host:port and wait for debugger to connect before running user code.
The REPL provides a couple of special variables, that are always available:
| Identifier | Description |
|---|---|
| _ | Yields the last evaluated expression |
| _error | Yields the last thrown error |
Deno 1.14.3
exit using ctrl+d or close()
> "hello world!"
"hello world!"
> _
"hello world!"
> const foo = "bar";
undefined
> _
undefined
The REPL provides several functions in the global scope:
| Function | Description |
|---|---|
| clear() | Clears the entire terminal screen |
| close() | Close the current REPL session |
--eval flag --eval flag allows you to run some code in the runtime before you are dropped into the REPL. This is useful for importing some code you commonly use in the REPL, or modifying the runtime in some way:
$ deno repl --allow-net --eval 'import { assert } from "jsr:@std/assert@1"'
Deno 1.45.3
exit using ctrl+d, ctrl+c, or close()
> assert(true)
undefined
> assert(false)
Uncaught AssertionError
at assert (https://jsr.io/@std/assert/1.0.0/assert.ts:21:11)
at :1:22
--eval-file flag --eval-file flag allows you to run code from specified files before you are dropped into the REPL. Like the --eval flag, this is useful for importing code you commonly use in the REPL, or modifying the runtime in some way.
Files can be specified as paths or URLs. URL files are cached and can be reloaded via the --reload flag.
If --eval is also specified, then --eval-file files are run before the --eval code.
$ deno repl --eval-file=https://docs.deno.com/examples/welcome.ts,https://docs.deno.com/examples/local.ts
Download https://docs.deno.com/examples/welcome.ts
Welcome to Deno!
Download https://docs.deno.com/examples/local.ts
Deno 1.45.3
exit using ctrl+d or close()
> local // this variable is defined locally in local.ts, but not exported
"This is a local variable inside of local.ts"
If --eval-file specifies a code file that contains relative imports, then the runtime will try to resolve the imports relative to the current working directory. It will not try to resolve them relative to the code file's location. This can cause "Module not found" errors when --eval-file is used with module files:
$ deno repl --eval-file=https://jsr.io/@std/encoding/1.0.0/ascii85.ts
error in --eval-file file https://jsr.io/@std/encoding/1.0.0/ascii85.ts. Uncaught TypeError: Module not found "file:///home/_validate_binary_like.ts".
at async :2:13
Deno 1.45.3
exit using ctrl+d or close()
>
Tab completions are crucial feature for quick navigation in REPL. After hitting tab key, Deno will now show a list of all possible completions.
$ deno repl
Deno 1.45.3
exit using ctrl+d or close()
> Deno.read
readTextFile readFile readDirSync readLinkSync readAll read
readTextFileSync readFileSync readDir readLink readAllSync readSync
| Keystroke | Action |
|---|---|
| Ctrl-A, Home | Move cursor to the beginning of line |
| Ctrl-B, Left | Move cursor one character left |
| Ctrl-C | Interrupt and cancel the current edit |
| Ctrl-D | If line is empty, signal end of line |
| Ctrl-D, Del | If line is not empty, delete character under cursor |
| Ctrl-E, End | Move cursor to end of line |
| Ctrl-F, Right | Move cursor one character right |
| Ctrl-H, Backspace | Delete character before cursor |
| Ctrl-I, Tab | Next completion |
| Ctrl-J, Ctrl-M, Enter | Finish the line entry |
| Ctrl-K | Delete from cursor to end of line |
| Ctrl-L | Clear screen |
| Ctrl-N, Down | Next match from history |
| Ctrl-P, Up | Previous match from history |
| Ctrl-R | Reverse Search history (Ctrl-S forward, Ctrl-G cancel) |
| Ctrl-T | Transpose previous character with current character |
| Ctrl-U | Delete from start of line to cursor |
| Ctrl-V | Insert any special character without performing its associated action |
| Ctrl-W | Delete word leading up to cursor (using white space as a word boundary) |
| Ctrl-X Ctrl-U | Undo |
| Ctrl-Y | Paste from Yank buffer |
| Ctrl-Y | Paste from Yank buffer (Meta-Y to paste next yank instead) |
| Ctrl-Z | Suspend (Unix only) |
| Ctrl-_ | Undo |
| Meta-0, 1, ..., - | Specify the digit to the argument. – starts a negative argument. |
| Meta < | Move to first entry in history |
| Meta > | Move to last entry in history |
| Meta-B, Alt-Left | Move cursor to previous word |
| Meta-Backspace | Kill from the start of the current word, or, if between words, to the start of the previous word |
| Meta-C | Capitalize the current word |
| Meta-D | Delete forwards one word |
| Meta-F, Alt-Right | Move cursor to next word |
| Meta-L | Lower-case the next word |
| Meta-T | Transpose words |
| Meta-U | Upper-case the next word |
| Meta-Y | See Ctrl-Y |
| Ctrl-S | Insert a new line |
DENO_REPL_HISTORY By default, Deno stores REPL history in a deno_history.txt file within the DENO_DIR directory. The location of your DENO_DIR directory and other resources, can be found by running the deno info.
You can use DENO_REPL_HISTORY environmental variable to control where Deno stores the REPL history file. You can set it to an empty value, Deno will not store the history file.
© 2018–2025 the Deno authors
Licensed under the MIT License.
https://docs.deno.com/runtime/reference/cli/repl