Asar electron “tarball”

# Open terminal and install asar node module globally
$ npm install -g asar
# Go into the app’s directory, in our case it’s Slack
$ cd /Applications/
# Create a directory to paste the content of app
$ mkdir example-sourcecode
# Unpack the app.asar file in the above directory using asar
$ asar extract app.asar example-sourcecode
# Boom cd into it and see the source code of the app