CODEWITHSUNDEEP
javascriptalgorithm
edmamerto
edmamerto

Reputation: 8165

Counting repeated values in array Javascript

I am trying to practice my algorithm skills. I know there is already an algorithm written out there, I just want to try it on my own and see how close i could get.

INPUT:

arr1 = ['asd','ew','lol','asd']

EXPECTED OUTPUT:

{ asd: 2, ew: 1, lol: 1 }

This is my code:

arr1 = ['asd', 'ew', 'lol', 'asd']
arr2 = []
results = {}

function checkIfExists(word) {
  if (arr2.length != 0) {
    for (i = 0; i < arr2.length; i++) {
      if (arr2[i] == word) {
        results[word] += 1
      } else {
        arr2.push(word)
        results[word] = 1
      }
    }
  } else {
    arr2.push(word)
    results[word] = 1
  }
}

for (i = 0; i < arr1.length; i++) {
  checkIfExists(arr1[i])
}
console.log(results)

ACTUAL OUTPUT:

{ asd: 2, ew: 2 }

Upvotes: 0

Views: 68

Answers (2)

autistic
autistic

Reputation: 15642

There are three questions I identified immediately which you might have intended to ask.

  1. What's wrong with my code?
    • I couldn't phrase this better than Felix Klings comment:

      The first problem is that you are not using var to declare i.

    • The loop presumably intended to locate an item within arr2 also modifies arr2... a lot!
  2. Why is my code producing incorrect output? Your code is actually producing correct output for the logic it expresses. I suspect the issue is that the logic it expresses doesn't match the logic you intended to express. This isn't uncommon
  3. How do I fix my code?
    • Start by changing your loop idioms from for (i = ...) to for (var i = ...).
    • Think about the purpose of that loop. If it's intended to locate an item within arr2, then it shouldn't need to modify arr2 to do so. Perhaps you don't need the loop;
      1. You could probably use Array.prototype.indexOf or Array.prototype.includes in place of that entire loop!
      2. You could probably use function checkIfExists(word) { results[word] = arr1.filter(function(w) { return w === word; }).length; } in place of that entire function!
      3. It seems like you could use some higher-level awareness when designing functions, so perhaps it might be a good idea to try to wrap your head around some of the elements in this code:
var arr1 = ['asd','ew','lol','asd'];
var result = arr1.reduce(function(result, w) { result[w] = result[w] || 0;
                                               result[w]++;
                                               return result;              }, {}));
console.log(result);

Upvotes: 1

Mohammad Hamedani
Mohammad Hamedani

Reputation: 3354

You used i as a global variable, so don't use for two loop. Other mistake is in your increment algorithm that add more than needed count to results array. So try it:

arr1 = ['asd','ew','lol','asd']
arr2 = [] 
results = {}

function checkIfExists(word){
    if (arr2.length != 0){
    	var exists = false;
      for (var j = 0; j < arr2.length; j++){
        if(arr2[j] == word){
          results[word] += 1
          exists = true;
          break;          
        }
      }
      if(!exists) {
          arr2.push(word)
          results[word] = 1
        }
    }else{
      arr2.push(word)
       results[word] = 1 
    }
}

for (var i = 0; i < arr1.length; i++) {
    checkIfExists(arr1[i])
}
console.log(results)

Upvotes: 2

Related Questions