JavaScript: accessing elements in an array

When inputting "12314" into the 'word' string below, everything functions correctly. However, if I enter characters like "abacd", the code encounters an error. Does anyone know why this might be happening? (1 in [1,2,3,1,4]) yields the correct result, but ('a' in [a,b,a,c,d] fails. I am still learning Javascript and would appreciate any insights.

var word = "abacd";

function duplicateEncode(word){

  var repeat = [];
  var result = [];
  var letters = word.split('');

  for (i=0; i < letters.length; i++){
    if (letters[i] in repeat) {
        result.push(")");
    } else {
        result.push("(");
    }
    repeat.push(letters[i]);
  }
  return result;
}
javascriptarrayscharacter

Answer №1

in operator:

A string or symbol representing a property name or array index (non-symbols will be coerced to strings).

Your situation works because it focuses on the index rather than the value of the string. When 'in' operator is used on an array, it considers the index as the properties.

Experiment with this:

> 1 in [1,2] //-> true
> 1 in [1]   //-> false (only one item in the list)
> 1 in [2,2] // -> true


> Object.keys([2,3,4])  // -> ['0', '1', '2' ]
// In your case, you should use indexOf instead
>['a','b','c'],indexOf('a') -> 0
>['a','b','c'],indexOf('e') -> -1

To resolve your problem, replace in with:

for (i=0; i < letters.length; i++){
 if (repeat.indexOf(letter[i]) > -1) {
    result.push(")");
 } else {
    result.push("(");
 }
 repeat.push(letters[i]);
}

Answer №2

Take a look at this code snippet...

function encodeDuplicates(input){

  var repeatedChars = [];
  var resultArray = [];
  var characters = input.split('');
  
  for (var i=0; i < characters.length; i++){
      if (repeatedChars.indexOf(characters[i]) != -1) {
          resultArray.push(")");
      } else {
          resultArray.push("(");
      }
      repeatedChars.push(characters[i]);
   }
   
   return resultArray;
}

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