How can I loop over an array of objects without Object.keys()?

Question

I'm a beginner at JavaScript and I'm trying to solve this problem without Object.keys() or any regex. I have a working solution but I'm wondering if there's a better way to call on the object key within the array while still looping. If anyone has a way to do this that's basic please let me know.

Problem: Create a function called keyCount which accepts two parameters, an array of objects, and a string. The function should return a number which is the number of times that key appears in the array of objects.

Expected Result: countTimesOfKey([{name:"Sharon"}, {name: "Manish"},{lastName: "Terma"}], "name")) // 2

My Answer:

function countTimesOfKey(arr, str) {
  let count = 0

  for (let i in arr){
    let test = arr[i]
    let test2 = test[str]

   if (test2 !== undefined){
      count += 1
    }
  }
  return count
}

Answer 1

You can use Array.filter to filter out the items in the array which have str as a property (by using Object.hasOwnProperty), then return the length of the resulting array:

function countTimesOfKey(arr, str) {
  return arr.filter(e => e.hasOwnProperty(str)).length;
}

console.log(countTimesOfKey([{
  name: "Sharon"
}, {
  name: "Manish"
}, {
  lastName: "Terma"
}], "name"))