ESMeta is an ECMAScript Specification Metalanguage. This framework extracts a mechanized specification from a given version of ECMAScript specification (ECMA-262) and automatically generates language-based tools.

Details of the ESMeta are available in our papers:

• [ASE 2020] JISET: JavaScript IR-based Semantics Extraction Toolchain [old repo]
• [ICSE 2021] JEST: N+1-version Differential Testing of Both JavaScript Engines [old repo]
• [ASE 2021] JSTAR: JavaScript Specification Type Analyzer using Refinement [old repo]
• [ESEC/FSE 2022] Automatically Deriving JavaScript Static Analyzers from Specifications using Meta-Level Static Analysis [old repo]

Title: Filling the gap between the JavaScript language specification and tools using the JISET family

• Session 1 by Jihyeok Park
• Session 2 by Seungmin An

We explain how to install ESMeta with necessary environment settings from the scratch. Our framework is developed in Scala, which works on JDK 8+, including GraalVM. Before installation, please install JDK 8+ and sbt, an interactive build tool for Scala.

$ git clone https://github.com/es-meta/esmeta.git

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

# for ESMeta
export ESMETA_HOME="<path to ESMeta>" # IMPORTANT!!!
export PATH="$ESMETA_HOME/bin:$PATH" # for executables `esmeta` and etc.
source $ESMETA_HOME/.completion # for autocompletion

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

$ cd esmeta && git submodule update --init && sbt assembly

You can run this framework with the following command:

$ esmeta <command> <option>*

with the following commands:

• help shows the help message.
• extract extracts specification model from ECMA-262 (ecma262/spec.html).
• compile compiles a specification to an IR program.
• build-cfg builds a control-flow graph (CFG) from an IR program.
• parse parses a JavaScript file.
• eval evaluates a JavaScript file.
• web starts a web server for interactive execution.

and global options:

• -silent does not show final results.
• -debug turns on the debug mode.
• -log turns on the logging mode.
• -time displays the duration time.

We will import the conformance test synthesizer we developed in JEST.

We will import the type analyzer for ECMA-262 we developed JSTAR.

We will import the meta-level static analyzer for ECMAScript we developed JSAVER.

ECMAScript Double Debugger extends the JavaScript interpreter in ESMeta to help you understand how a JavaScript Program runs according to ECMA-262. Currently, it is in an alpha stage and supports only basic features such as:

• Step-by-step execution of ECMAScript
• Breakpoints by abstract algorithm names in ECMAScript
• Visualization of states like a call stack, an environment, and a heap of ECMAScript
• Line-by-line execution of JavaScript

You can start it with the following instructions:

# turn on server of the double debugger
$ esmeta web

# install the client-side application using NPM
$ git clone https://github.com/es-meta/esmeta-debugger-client.git
$ cd esmeta-debugger-client
$ npm i

# turn on the client-side application
$ npm start

A short introduction video is also available.

We will enhance it with the following features:

• Add more debugger features:
  • Show a JavaScript state by refining an ECMAScript state.
  • Record timestamps during execution for resume & suspend steps (especially for Generator).
  • ...
• Show relevant Test262 tests for each algorithm step in the specification viewer.
• Show the type of each variable using the type analysis result of JSTAR.
• Live-edit of ecma262/spec.html in the specification viewer.