First Class Function

• Function can be used as value like storing in variable, passing as arguments, returning as value.

HOF

High Order Function is a function that either:

• takes one or more functions as arguments.
• returns a function as its result.

Common HOF in Javascript:

• map()
• filter()
• reduce()
• forEach()
• sort()

Custom HOF

Example:

const performOperation = (operation) => {
  console.log("Operation Request Accepted");
  return operation;
};
const add = (a, b) => {
  return a + b;
};
const addOperation = performOperation(add);
console.log(addOperation(4, 5));

performOperation is a HOF