JSFiddle - React, Tailwind, and code Playground

JavaScript

function add (a,b){return a+b;}
function multiply (a,b){return a*b;}

function applyFn(callback) {
    return callback;
};

var f = applyFn(add);

console.log(f); //logs => function add(a,b){return a+b;}

alert(f(3, 4)); // returns => Uncaught TypeError: f(...) is not a function(…)