“Universal JavaScript” is used to describe JavaScript code that “can execute on the client and the server”.

References

• https://medium.com/@mjackson/universal-javascript-4761051b7ae9

Semantic commit message is a commit message format which helps to write better commit message.

References

• http://stackoverflow.com/questions/26944762/when-to-use-chore-as-type-of-commit-message
• https://seesparkbox.com/foundry/semantic_commit_messages
• https://github.com/fteem/git-semantic-commits

A software regression is a software bug which makes a feature to stop functioning as intended after a certain event, for example a system upgrade, system patching.

One approach to avoiding this kind of problem is regression testing.

References

• https://en.wikipedia.org/wiki/Software_regression
• https://en.wikipedia.org/wiki/Regression_testing
• http://stackoverflow.com/questions/3464629/what-does-regression-test-mean

Functions that operate on other functions, either by taking them as arguments or by returing them, are called higher order functions.

function expression(name) {
    return function() {
        console.log(name);
    }
}

let smile = expression('smile');
let laugh = expression('laugh');

smile(); // prints 'smile'
laugh(); // prints 'laugh'

References

• Higher-Order Functions
• Higher-Order Functions in JavaScript
• The Rise and Fall and Rise of Functional Programming

NODE_ENV is an environment variable made popular by the Express.js framework. It is specifically used to state whethere a particular environment is production or development.

var environment = process.env.NODE_ENV

References

• http://stackoverflow.com/questions/16978256/what-is-node-env-in-express