does .filter has built in return ? code example

Example 1: how the filter() function works javascript

const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];

const filter = arr.filter((number) => number > 5);
console.log(filter); // [6, 7, 8, 9]

Example 2: javascript object filter

function objectFilter = (obj, predicate) => 
    Object.keys(obj)
          .filter( key => predicate(obj[key]) )
          .reduce( (res, key) => (res[key] = obj[key], res), {} );

// Example use:
var scores = {
    John: 2, Sarah: 3, Janet: 1
};

var filtered = objectFilter(scores, num => num > 1); 
console.log(filtered);

Example 3: javascript array filter

run.addEventListener("click", function () {
    let array = [];
    people.forEach((elem) => {
      // elem before age to target
      if (elem.age > 18) {
        array.push(elem); // each array elem > 18 is "pushed" inside the new array
        // console.log(array); nope : messes things up
      } else {
        (""); // no need to declare this through console.log
      }
    });
    console.log(array); //and there you have it : filtered array
  });