filterMapReduce.js

// this is a demo on how to use the filter map and reduce
// we are also going to e learning on how to chain them together

const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, "9", false, "new test", "awesome code"];
console.log("\n==========Original Array============== \n");
console.log(arr);
console.log("\n");

let filteredArray = arr.filter(
  (x) => typeof parseInt(x) == "number" && x % 2 == 1
);

// this will give an empty array because the difference between the
// "==" which is an equality operator check && "===" is identity operator check
// if used the == it should use false as 0 and true as 1
// in case of === it should give a [] empty array since the the values inside the array dont match the type

//filter function is basically a condition check which can be applied to every individual item in the array
//or list and reduces it to the element which have met the conditions truely
// we can also filter the string aswell if desired

//console.log(arr.filter(x=> (x%2 == false)|| (typeof(x) == "string")));

console.log(
  "===============filtered array of odd numbers====================== \n"
);
console.log(filteredArray + "\n\n");

//mapping works on all the elements of the array and does a certain task, here to square

let mappedArray = filteredArray.map((x) => x * x);
console.log(
  "============mapped array of square of odd numbers================= \n"
);
console.log(mappedArray + "\n\n");

// reduces does as the name suggests, to reduce the list into one

let reducedArray = mappedArray.reduce((x, y) => x + y);
console.log(
  "=======reduced array of addition of squares of odd numbers======== \n"
);
console.log(reducedArray + "\n\n");

// using chaining method can also help us achieve similar results
// code above is equivalent to the code below
let filteredMapReducedArray = arr
  .filter((x) => typeof parseInt(x) === "number" && x % 2 === 1)
  .map((x) => x * x)
  .reduce((x, y) => x + y);

console.log(filteredMapReducedArray);