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
}

Spectric · Accepted Answer · 2021-09-02 19:23:17Z

2

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"))

answered Sep 2, 2021 at 19:23

Spectric

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0stone0 · Accepted Answer · 2021-09-02 19:32:59Z

Of course, using Object.keys() and @Spectric's solution are way better than the one below, I just wanted to show that we can even more 'simplify' this.

We can use for...in to

Loop over each object in the array
Loop over each key of the object on the current index
- Compare the name of each key against our check variable
  - Increase our counter
return the result counter

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

function countTimesOfKey(arr, name) {
    let counter = 0;
    for (a in arr) {
        for (let k in arr[a]) {
            if (k === name) {
                counter++;
            }
        }
    }
    return counter;
}

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