first-class-function.md

First Class Function

Functions which behaves and can be used like any other variable in the program are called as first class functions. For example a function can be an argument to some function call like any other variable passed as any agrument.

Here function square is passed as an argument to the transform function.

function square(x) {
  return x * x;
}

function transform(x, postTransform) {
  const y = x + 1;
  return postTransform(y);
}

transform(1, square); // 4