Functions – First-Class Citizens

Functions being first-class means they are considered by the language to be like any other "value" type. This means that, in JavaScript, a function can be used just like a number, a string, a Boolean, an array, an object, and so on.

Note

Now would probably be a good time to see how well-versed in JavaScript data types everyone is. The primitives are Boolean, Null, Undefined, Number, (BigInt), String, Symbol, Object à Array/Set/Map. They can be found under the Object data type.

First-Class Functions – Idiomatic JavaScript Building Blocks

Another way to define first-class support is as "functions are first-class if they are regular values." That means that a function can be assigned (as a value) to a variable, passed into other functions as a parameter, and be the return value of another function. Let's try and understand the preceding concept with code examples.

A function can be assigned to...