eloquentjavascript : chapter 4

file.js

const range = (start, end, step=1) => {
  const data = [];
  for(let i=start; i <= end; i=i+step) {
    data.push(i);
  }
  return data;
};

console.log(range(3,6));
console.log(range(1,100,10));

const sum = (numbers) => {
  return numbers.reduce((reduced, item) => reduced += item);
};

console.log(sum([1,2,3]));

console.log(sum(range(1, 10)));

const reverseArray = (data) => {
  return data.map((item, i) => data[data.length-(i+1)]);
};

let data = [1,2,3];
console.log(reverseArray(data));
// check we didn't mutate original data
console.log(data);

// tried to do something a little different and iterate over half the array so its faster
// and modify the head and tail of array as we loop
const reverseArrayInPlace = (data) => {
  for(let i=0; i < data.length/2; i++) {
    const newStartNum = data.slice(data.length-(i+1), data.length-(i+1)+1)[0];
    const newEndNum = data.slice(i, i+1)[0];
    data[i] = newStartNum;
    data[data.length-(i+1)] = newEndNum;
  }
  return data;
};

let data = [1,2,3,4,5,6];
console.log(reverseArrayInPlace(data));
// check we mutated original data
console.log(data);


function arrayToList(data) {
  if (!data.length) return null;
  const first = data.slice(0, 1)[0];
  const remaining = data.slice(1, data.length);
  return {value: first, rest:arrayToList(remaining) };
};

console.log(arrayToList([10, 20]));

function listToArray(obj, data = []) {
  data.push(obj.value);
  if(obj.rest) data = listToArray(obj.rest, data);
  return data;
};

console.log(listToArray(arrayToList([10, 20, 30])));

const prepend = (el, list) => {
};

console.log(prepend(10, prepend(20, null)));

const nth = (list, num) => {
  
};

console.log(nth(arrayToList([10, 20, 30]), 1));

output

// range
[3,4,5,6] 
// range with step
[1,11,21,31,41,51,61,71,81,91] 

// sum
6 

// sum range
55 

// reverse array
[3,2,1]
[1,2,3] // <!-- original input data didn't get modified yay

// reverse array inplace
[6,5,4,3,2,1] 
[6,5,4,3,2,1] // <!-- original input was modified yay

// array to list
{"value":10,"rest":{"value":20,"rest":null}} 

// list to array
[10,20,30] 

// prepend

// nth