d8

Start a REPL (interactive shell)

$ d8

$ d8 [path/to/file.js]

$ d8 -e "[code]"

d8 [options] [script.js] [-- args]

--help
    Print help and usage information.

--version
-v
    Print the V8 version string.

--print-ast
    Print the AST before compiling.

--print-code
-p
    Print generated machine code.

--allow-natives-syntax
    Allow inline runtime functions like %DebugPrint.

--harmony
    Enable all completed harmony features (deprecated).

--expose-gc
    Expose gc() function globally.

--max-old-space-size=size
    Max size of the old space (in Mbytes).

--trace-gc
    Trace garbage collections.

--interactive
-i
    Force interactive mode (REPL).

--shell-mode
    Similar to interactive but specialized.

--check
    Check script syntax only.

d8 is the command-line shell for Google's V8 JavaScript engine, extracted from Chromium. It allows direct execution of JavaScript code, scripts, or interactive REPL sessions without a browser environment.

Primarily used by developers for testing JavaScript performance, debugging engine behavior, and benchmarking. Supports ECMAScript standards, modules, and V8-specific features like native syntax for optimization inspection.

Invoke with a script file for batch execution or without arguments for REPL mode. Outputs results to stdout; errors to stderr. Highly configurable via flags mirroring V8's runtime options, enabling fine-tuned control over garbage collection, JIT compilation, and more.

Not installed by default on most Linux distributions; obtain via Chromium source builds, prebuilt binaries, or packages like chromium-d8 in some repos.

Not standard on most systems; requires manual installation. Hundreds of V8-specific flags exist (--help for full list); undocumented or experimental flags may change. High memory usage with large heaps.

d8 script.js runs JS file.
d8 -i starts REPL: > print('Hello');

On Ubuntu/Debian: apt install chromium-browser. Then /path/to/chrome --no-sandbox --dump-dom d8 or build from source.

Introduced with V8 in 2008 by Google. Evolved alongside Chromium; binaries from depot_tools or official builds. Key milestones: ES6 support (2015), ES2017+ features progressively added.

node(1), deno(1), v8(1)