deno repl, interactive scripting prompt

deno repl [OPTIONS] [-- [ARGS]...]

Options

--cert

Load certificate authority from PEM encoded file.

--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.

--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.

Dependency management options

--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Error out if lockfile is out of date.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.

Debugging options

--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.

Special variables

The REPL provides a couple of special variables, that are always available:

Deno 1.14.3
exit using ctrl+d or close()
> "hello world!"
"hello world!"
> _
"hello world!"
> const foo = "bar";
undefined
> _
undefined

Special functions

The REPL provides several functions in the global scope:

--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 <anonymous>: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"

Relative Import Path Resolution

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 <anonymous>:2:13
Deno 1.45.3
exit using ctrl+d or close()
>

Tab completions

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

Keyboard shortcuts

DENO_REPL_HISTORY

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.