Updating JerryScript

Currently we use Jerryscript version v2.4 from JerryScript, imported as a submodule.

The web-assembly (WASM) snapshot compiler uses the emscripten SDK.


In order to update the version of JerryScript two tasks have to be executed:

  • In this repository update the submodule version of JerryScript to point to the new version

  • Rebuild the snapshot compiler

The snapshot compiler can be rebuilt manually as follows:

  1. Install the emscripten SDK:

    git clone --depth 1 https://github.com/emscripten-core/emsdk.git emsdk
    emsdk/emsdk install latest
    emsdk/emsdk activate latest
  2. run make from the emscripten-snapshot-compiler directory.

The following three files are generated in emscripten-snapshot-compiler/build/bin/{PROFILE}:

  • jsc.js

  • jsc.wasm

  • jsc.wasm.map

Copy these to the jsc sub-directory for application use as demonstrated in the Advanced_Jsvm sample.


The snapshot compiler can be rebuilt using a Docker container which also includes a WebAssembly toolkit. It can be built and run with the following commands:

docker build -f Dockerfile -t jerryscript-ems .
docker run -it jerryscript-ems

Inside the container a new jerryscript snapshot compiler can be built by calling:

node /jerryscript/build/bin/minimal/jsc.js -o /tmp/test.js.snap /tmp/test.js

Where test.js.snap is the output file and /tmp/test.js is an existing JavaScript file.

To update the jsc.* files you run the following from the application directory:

docker run -v $(pwd)/files/web/:/web -it jerryscript-ems

And run the following commands inside the container:

cp -r /jerryscript/build/bin/minimal/jsc.* /web

The build system handles compilation of the main.js file, but if you prefer to use pre-compiled snaps this can also be done inside the container:

node /jerryscript/build/bin/minimal/jsc.js -o /web/main.js.snap /web/main.js