It’s time to get our hands dirty with Javascript. Now that you have heard about TDD, let see if we can transfer our learning to another world of Javascript.

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Setup and Getting Started

We have created a dummy project for you. You’ll need nodejs pre installed to run this. Please check if it's installed by running which node on your terminal which should give you the path of node. If instead it comes up with a message like node not found then you should look online on how to install node. As such brew install node should work (if you're using Mac).

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Running tests

After this, run the ./go.sh this should install any dependencies and then run the test. You should see one failing test and one passing test. Its good to get used to knowing how a passing/failing test looks with a particular tooling. Fix the test and move on to the next step.

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About the assignment

• In this assignment, we want you to understand that loops are an imperative way of programming. Usual use cases of loops can be classified as
  • Converting one collection to another collection - Typical use of map, return type is collection
  • Getting a subset of a collection - Typical use of filter, return type is collection.
  • Converting collection to a value - Typical use of reduce, return type maybe not a collection.

Keep in mind

• We want you to TDD and use Javascript to implement these functions.
• Avoid using loops in your implementation as much as possible.
  • Recursion is your friend
  • You can reuse a function that you have written yourself
• Make sure you have small commits (after each passing test and refactoring as necessary)

Functions to implement

• head - returns first element
  • e.g. head([1,2,3]) should be 1
  • e.g head([]) should be null or undefined
• tail - returns everything except first element
  • e.g. tail([1,2,3]) should be [2,3]
  • e.g tail([]) should be []
• map
  • e.g map([], cube) should give []
  • e.g map([1,2,3], identity) should give [1,2,3]
  • e.g.map([1,2,3], cube) should give [1,8,27]
  • e.g. map([a{x : 10}],someObject => someObject.x + 1) -> [11]
    • where identity and cube are functions
• filter
  • e.g filter([], x => true) should give []
  • e.g. filter([1,2,3],x => true) should give [1,2,3]
  • e.g. filter([1,2,3],x => false) should give []
  • e.g. filter([1,2,3],x => x > 1) should give [2,3]
  • e.g. filter(['a','B','c','D'], filterUpperCase) should be [B,D]
• reduce
  • e.g. reduce([],(x,y)=>x+y) should be undefined
  • e.g. reduce([],v(x,y)=>x+y,10) should be 10
  • e.g. reduce(['a','b','c'],(x,y)=>x+y) should be abc
  • e.g. reduce(['a','b','c'],(x,y)=>x+y,’z’), should be zabc
• max
  • e.g. max([1,2,3,4]) should be 4
• min
  • same as above... return 1