If any programming language has the ability to treat functions as values, to pass them as arguments and to return a function from another function then it is said that programming language has First Class Functions and the functions are called as First Class Citizens in that programming language.
Functions are very important and powerful in JavaScript.
JavaScript has all those abilities or features that are required to be a language having First Class Functions, hence functions are treated as First Class Citizens.
Let’s look at all the abilities of functions being a First Class Citizen.