iterate , iterate, iterate

Lets cut to the chase and look at what we are trying to do here. We need to write a function that can spit an array of any given size, such that every element is obtained by applying a function on the previous element.

Let us consider an initial element x and a function f, what we need is an array which looks something like this :

[x, f(x), f(f(x)), ...]

Well, the simplest application of such a function would be to create a series of numbers like , squares of 2 : 1 ,2, 4, 8 ..

Now lets look at how we can write such a function

function iterate(fn, ele, n) {
  if (n === 0) return [];
  return [ele, ...iterate(fn, fn(ele), n - 1)];
}

Our function iterate, returns a list of repeated applications of fn to ele, repeated n number of times:
Lets try out some examples

This code block is no longer available. The original code is shown below.

    
function iterate(fn, ele, iterationCount) {
  if (iterationCount === 0) return [];
  return [ele, ...iterate(fn, fn(ele), iterationCount - 1)];
}

  

    
const multiply = (x) => (y) => x * y;
console.log(iterate(multiply(2), 1, 5));

  

The initial item and the function you apply can be anything that you can think of. You could easily create a list of dummy products take a look at the example:

This code block is no longer available. The original code is shown below.

    
function iterate(fn, ele, iterationCount) {
  if (iterationCount === 0) return [];
  return [ele, ...iterate(fn, fn(ele), iterationCount - 1)];
}

  

    

const initialProduct = { id: 100, slug: `prd${100}`, name: `Product-${100}` };

const createNextProduct = (product) => {
  const nextProductId = product.id + 1;
  return {
    id: nextProductId,
    slug: `prd${nextProductId}`,
    name: `Product-${nextProductId}`,
  };
};
console.log(iterate(createNextProduct, initialProduct, 5));