StartSource · quickjs-oxide@4e549ac9

Use the qjs command line

qjs is quickjs-oxide's command line. It follows the qjs of QuickJS 2026-06-04: the same usage line, the same options for running scripts and modules, the same print, console.log and scriptArgs, the same error output and the same exit statuses. If you have used QuickJS's qjs, you already know this one; the differences are listed at the end of this page.

Install

Prebuilt binaries for Linux, macOS and Windows are attached to every GitHub release. With Rust installed, build it from the repository or fetch the prebuilt binary through cargo-binstall:

shell
cargo install --locked --git https://github.com/pocket-nexus/quickjs-oxide quickjs-oxide-cli
cargo binstall --git https://github.com/pocket-nexus/quickjs-oxide quickjs-oxide-cli
shell
qjs --version
# quickjs-oxide 0.3.1 (QuickJS 2026-06-04 compatibility target)

Run a script

usage: qjs [options] [file [args]]

qjs runs file and passes the arguments after it to the script as scriptArgs, with the file name first:

js
// main.js
import { x } from "./lib.mjs";
console.log(x * 2, scriptArgs.join("|"));
shell
qjs main.js a b        # 42 main.js|a|b

As in QuickJS, a file is loaded as an ES module when its name ends in .mjs or its source uses import or export, and as a script otherwise. -m / --module and --script force one or the other. Modules are loaded from the file system relative to the importing file.

Evaluate an expression

-e evaluates its argument instead of a file. --print-result prints the completion value of the script:

shell
qjs -e 'print(6 * 7)'              # 42
qjs --print-result -e '6 * 7'      # 42

Errors and exit status

An uncaught exception prints the error and its stack, the way QuickJS prints it, and exits with status 1:

shell
qjs -e 'null.length'
# TypeError: cannot read property 'length' of null
#     at <eval> (<cmdline>:1:5)

A promise that is rejected and never handled prints Possibly unhandled promise rejection: and exits with status 1; --no-unhandled-rejection ignores such rejections. Status 0 means the script and every job it queued completed. An unknown option prints the usage text and exits with status 2.

Options

Option Effect
-e, --eval EXPR evaluate EXPR
-m, --module load as an ES module
--script load as a script
-s strip all debug information
--strip-source strip only function source text
--no-unhandled-rejection ignore unhandled promise rejections
--print-result print the script's completion value
-q, --quit create the runtime and exit
--std define the load(file) and read(file) globals
-v, --version show the version and the QuickJS version it targets
-h, --help show the usage text

Memory and measurement

Option Effect
--heap-cap-mib N cap the heap at N MiB; past it, allocation throws InternalError: out of memory
--min-heap-mib N the collector's minimum heap budget (default 1)
--gc-growth F bytes allocated between collections per live byte (default 2)
--stack-limit N the number of registers the register file may hold
--gc-stats print the collector's statistics at exit
--memory-report print what every part of the runtime holds at exit
--disassemble print the register code of file and exit

Errors and limits explains the heap and collector settings, and Optimizations the register code that --disassemble prints.

Differences from QuickJS's qjs

QuickJS's qjs quickjs-oxide's qjs
--std makes the std and os modules available --std defines the load and read globals
--memory-limit n --heap-cap-mib N
-d (memory usage at exit) --memory-report
-i (interactive mode), -I (include a file), --strict, -T (trace allocations), --stack-size n not available
an unknown option exits with status 1 an unknown option exits with status 2

Where to go next