JSGen is a JavaScript Program Generator. It generalizes program generation techniques used in another tool JEST which is a N+1-version Differential Testing of both JavaScript engines and specifications.

We explain how to install JSGen with necessary environment settings from the scratch. Before installation, please download JDK 8 and sbt.

$ git clone https://github.com/f52985/jsgen.git

Insert the following commands to ~/.bashrc (or ~/.zshrc):

# for JSGen
export JSGEN_HOME="<path to JSGen>" # IMPORTANT!!!
export PATH="$JSGEN_HOME/bin:$PATH" # for executables `jsgen` and etc.
source $JSGEN_HOME/jsgen-auto-completion # for auto completion

The <path to JSGen> should be the absolute path of JSGen repository.

$ cd jsgen && git submodule init && git submodule update && sbt assembly

Extract and generate a model from ECMAScript 2021 (ES12 / es2021):

$ jsgen gen-model -extract:version=es2021
# ========================================
#  extract phase
# ----------------------------------------
# version: es2021
# parsing spec.html... (10,476 ms)
# ========================================
#  gen-model phase
# ----------------------------------------
# generating models... (240 ms)

Create the following JavaScript file sample.js:

// sample.js
var x = 1 + 2;
print(x);

Parse sample.js:

$ jsgen parse sample.js
# ========================================
#  parse phase
# ----------------------------------------
# var x = 1 + 2 ; print ( x ) ;

Evaluate sample.js:

$ jsgen eval sample.js -silent
# 3.0

Show detail path and final results during evaluation of sample.js:

$ jsgen eval sample.js -debug

You can run the artifact with the following command:

$ jsgen <sub-command> <option>*

with the following sub-commands:

• help shows the help message.
• extract extracts ECMAScript model from ecma262/spec.html.
• gen-model generates ECMAScript models.
• compile-repl performs REPL for printing compile result of particular step.
• gen-test generates tests with the current implementation as the oracle.
• parse parses a JavaScript file using the generated parser.
• load loads a JavaScript AST to the initial IR states.
• eval evaluates a JavaScript file using generated interpreter.
• filter-meta extracts and filters out metadata of test262 tests.
• parse-ir parses an IR file.
• load-ir loads an IR AST to the initial IR states.
• eval-ir evaluates an IR file.
• repl-ir performs REPL for IR instructions.
• build-cfg builds control flow graph (CFG).

and global options:

• -silent does not show final results.
• -debug turns on the debug mode.
• -interactive turns on the interactive mode.
• -no-bugfix uses semantics including specification bugs.
• -time displays the duration time.