diff --git a/subjects/block-chain.en.md b/subjects/block-chain.en.md new file mode 100644 index 000000000..a5e5e392f --- /dev/null +++ b/subjects/block-chain.en.md @@ -0,0 +1,64 @@ +## Block Chain + +### Instructions + +Create a `blockChain` that create a block in your very own block chain. + +the function takes 2 arguments: +- `data` any valid JSON data +- `prev` the previous block, if no block are given it should use the + genesis block: `{ index: 0, hash: '0' }` + +A block must have the following properties: +- `index` +- `hash` a computed hash using the concatenation of the `index`, `hash` + and stringified `data` and hashing all of it using the provided `hashCode`. +- `data` the data (not encoded in JSON) +- `prev` the previous block +- `chain` a function that takes a new `data` and create the next block with it. + + +### Examples + +```js +const first = blockChain({ a: 1 }) +console.log(first.index) // -> 1 +console.log(first.data) // -> { a: 1 } +console.log(first.prev) // -> { index: 0, hash: "0" } +console.log(first.hash) // -> '1103f27' +console.log(hashCode('10{"a":1}')) // -> '1103f27' + +const second = first.chain({ hello: 'world' }) +console.log(second.hash) // -> '18drvvc' +console.log(hashCode('21103f27{"hello":"world"}')) // -> '18drvvc' + +const chain = second + .chain({ value: 4455 }) + .chain({ some: 'data' }) + .chain({ cool: 'stuff' }) + +const fork = second + .chain({ value: 335 }) + .chain({ some: 'data' }) + .chain({ cool: 'stuff' }) + +console.log(chain.hash) // -> '1qr3qfs' +console.log(fork.hash) // -> '1x9gsc1' +console.log(chain.index) // -> 5 +console.log(fork.index) // -> 5 +``` + + +### Notions + +- [devdocs.io/javascript/global_objects/json/stringify](https://devdocs.io/javascript/global_objects/json/stringify) + + +### Code provided + +```js +const hashCode = str => + ( + [...str].reduce((h, c) => (h = (h << 5) - h + c.charCodeAt(0)) & h, 0) >>> 0 + ).toString(36) +``` diff --git a/subjects/collections.en.md b/subjects/collections.en.md new file mode 100644 index 000000000..e647da300 --- /dev/null +++ b/subjects/collections.en.md @@ -0,0 +1,72 @@ +## Collections + +### Instructions + +Write a bunch of function to move from one type to another + +- `arrToSet` from `Array` to `Set` +- `arrToStr` from `Array` to `String` +- `setToArr` from `Set` to `Array` +- `setToStr` from `Set` to `String` +- `strToArr` from `String` to `Array` +- `strToSet` from `String` to `Set` +- `mapToObj` from `Map` to `Object` +- `objToArr` from `Object` to `Array` +- `objToMap` from `Object` to `Map` +- `arrToObj` from `Array` to `Object` +- `strToObj` from `String` to `Object` + +and finally write a function `superTypeOf` that unlike `typeof` return +a different value for advanced types like `Map` and `Set` + + +### Examples + +```js +const str = 'hello' +const arr = [ 1, 2, 1, 3 ] +const obj = { x: 45, y: 75, radius: 24 } +const set = new Set() +const map = new Map() +set.add(1) +set.add(2) +set.add(1) +set.add(3) +map.add('a', 1) +map.add('b', 2) +map.add(3, 'c') +map.add(4, 'd') + +arrToSet(arr) // -> Set { 1, 2, 3 } +arrToStr(arr) // -> '1213' +setToArr(set) // -> [1, 2, 3] +setToStr(set) // -> '123' +strToArr(str) // -> ['h', 'e', 'l', 'l', 'o'] +strToSet(str) // -> Set { 'h', 'e', 'l', 'o' } +mapToObj(map) // -> { a: 1, b: 2, '3': 'c', '4': 'd' } +objToArr(obj) // -> [45, 75, 24] +objToMap(obj) // -> Map { 'x' => 45, 'y' => 75, 'radius' => 24 } +arrToObj(arr) // -> { '0': 1, '1': 2, '3': 1, '4': 3 } +strToObj(str) // -> { '0': 'h', '1': 'e', '2': 'l', '3': 'l', '4': 'o' } + +superTypeOf(map) // -> 'Map' +superTypeOf(set) // -> 'Set' +superTypeOf(obj) // -> 'Object' +superTypeOf(str) // -> 'String' +superTypeOf(666) // -> 'Number' +superTypeOf(NaN) // -> 'Number' +superTypeOf(arr) // -> 'Array' +superTypeOf(null) // -> 'null' +superTypeOf(undefined) // -> 'undefined' +superTypeOf(superTypeOf) // -> 'Function' +``` + + +### Notions + +- [devdocs.io/javascript/operators/typeof](https://devdocs.io/javascript/operators/typeof) +- [devdocs.io/javascript/operators/spread_syntax](https://devdocs.io/javascript/operators/spread_syntax) +- [devdocs.io/javascript/global_objects/map](https://devdocs.io/javascript/global_objects/map) +- [devdocs.io/javascript/global_objects/set](https://devdocs.io/javascript/global_objects/set) +- [devdocs.io/javascript/global_objects/object/fromentries](https://devdocs.io/javascript/global_objects/object/fromentries) +- [devdocs.io/javascript/global_objects/object/entries](https://devdocs.io/javascript/global_objects/object/entries)