Can you give examples of first-class functions?

What are first-class functions?

First-class functions are functions that can be treated like any other variable. They can be assigned to variables, passed as arguments, or returned from other functions.

Can you give me some examples of first-class functions?

Sure! In JavaScript, you can assign a function to a variable like this:

const greet = function() { return 'Hello!'; }

You can also pass functions as arguments:

function callFunction(fn) { fn(); }
callFunction(greet);

Are there any programming languages that don't support first-class functions?

Yes, some older languages like COBOL and Fortran do not support first-class functions. However, most modern languages like JavaScript, Python, and Ruby do.