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# Prasannavk94's solution

## to Accumulate in the TypeScript Track

Published at Jun 24 2020 · 0 comments
Instructions
Test suite
Solution

Implement the `accumulate` operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.

Given the collection of numbers:

• 1, 2, 3, 4, 5

And the operation:

• square a number (`x => x * x`)

Your code should be able to produce the collection of squares:

• 1, 4, 9, 16, 25

Check out the test suite to see the expected function signature.

## Restrictions

Keep your hands off that collect/map/fmap/whatchamacallit functionality provided by your standard library! Solve this one yourself using other basic tools instead.

## Setup

Go through the setup instructions for TypeScript to install the necessary dependencies:

https://exercism.io/tracks/typescript/installation

## Requirements

Install assignment dependencies:

``````\$ yarn install
``````

## Making the test suite pass

Execute the tests with:

``````\$ yarn test
``````

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by changing `xit` to `it`.

## Source

Conversation with James Edward Gray II https://twitter.com/jeg2

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### accumulate.test.ts

``````import accumulate from './accumulate'

describe('accumulate()', () => {
it('accumulation empty', () => {
const accumulator = (e: number): number => e * e
expect(accumulate([], accumulator)).toEqual([])
})

it('accumulate squares', () => {
const accumulator = (n: number): number => n * n
const result = accumulate([1, 2, 3], accumulator)
expect(result).toEqual([1, 4, 9])
})

it('accumulate upcases', () => {
const accumulator = (word: string): string => word.toUpperCase()
const result = accumulate('hello world'.split(/\s/), accumulator)
expect(result).toEqual(['HELLO', 'WORLD'])
})

it('accumulate reversed strings', () => {
const accumulator = (word: string): string => word.split('').reverse().join('')
const result = accumulate('the quick brown fox etc'.split(/\s/), accumulator)
expect(result).toEqual(['eht', 'kciuq', 'nworb', 'xof', 'cte'])
})

it('accumulate recursively', () => {
const result = accumulate('a b c'.split(/\s/), (char: string) => accumulate('1 2 3'.split(/\s/), (digit: string) => char + digit))

expect(result).toEqual([['a1', 'a2', 'a3'], ['b1', 'b2', 'b3'], ['c1', 'c2', 'c3']])
})
})``````
``````export default function accumulate<T, U>(
data: T[],
accumulator: (arg: T) => U
): U[] {
const result: U[] = [];
data.forEach((value) => {
result.push(accumulator(value));
});
return result;
}``````

### What can you learn from this solution?

A huge amount can be learned from reading other peopleâ€™s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

• What compromises have been made?