In .travis.yml, we must first specify the primary language our project is written in. This allows Travis to install the required dependencies, and use appropriate default settings and configurations. For example, if we specify that our project is written in Node.js, Travis will, by default, configure itself to install dependencies by running npm install, and test the application by running npm test. It'll also look for a yarn.lock file at the root directory, and if it's present, use the yarn install and yarn run test commands instead.
Therefore, add the following line inside our .travis.yml file to inform Travis that this project uses Node.js:
language: node_js
With Node.js, you can also specify which version of Node.js ...
