Passing functions to map

functionstomap.js

const myAnimals = ['dog', undefined, 'cat', 'bird', undefined, 0, false];

myAnimals.filter(Boolean); // Result: ['dog', 'cat', 'bird'];

/* 
    it will call Boolean('dog'), then Boolean(undefined), 
    then Boolean('cat') etc etc, the array.filter() callback must return true to keep
    an element in the array, if its false it excludes it
*/

const myValues = [1.34, 3.5, 3.6, 4.1];

// now using Math.round() on .map()
myValues.map(Math.round) // [1, 4, 4, 4];