Wherefore art thou(Problem)

Curriculum Help
1

Could not go any further
Right in this code the algorithm is specific ,(in the sense only works with parameters given)
How to make it general (works for any values given in the paramters)

console.clear()

function whatIsInAName(collection, source) {
  // What's in a name?
  var arr = []
  // Only change code below this line
  let collectionArr = collection
  let sourceArr = source
  let Arr = []
  for(let pos in sourceArr) {
    //console.log(pos)
    Arr.push(pos)
  }
  for(let i = 0;i<collectionArr.length;i++) {
    //console.log(collectionArr[i])
    if(collectionArr[i][Arr[i]] === sourceArr[Arr[i]]) {
      //console.log(collectionArr[i])
      //console.log(collectionArr[i][Arr[0]])
      //console.log(collectionArr[i])
      arr.push(collectionArr[i])
    }
  }
  let filteredArr = arr.filter((list) => {
    //console.log()
    if(list[Arr]) {
      return true
    }
    else {
      return false
    }
  })
  //console.log(filteredArr)
  // Only change code above this line
  return filteredArr
}

console.log(whatIsInAName([{ first: "Romeo", last: "Montague" }, { first: "Mercutio", last: null }, { first: "Tybalt", last: "Capulet" }], { last: "Capulet" }))
2

What do the failing tests say? What else have you tried? What steps have you taken to try to find the problem?