Javascript: character in array

Question

If I enter "12314" in the 'word' string below, everything works as intended. If I enter characters such as "abacd", the code fails. Can anyone tell me why? (1 in [1,2,3,1,4]) works, but ('a' in [a,b,a,c,d] fails. I'm fairly new to Javascript.

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;
}

I'm looking for "(" the first time a character is encountered in the string and ")" if it's already been found. "abacd" should return "(()((" and "12314" should return "((()(". — James Beau
– James Beau, Commented Sep 14, 2016 at 12:32

Nix · Accepted Answer · 2016-09-14 12:41:56Z

1

in operator:

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

In your case it's working because its looking at the index not the value of the string. When using the 'in' operator on an array its using the index as the properties

Play around 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 would want to use indexOf
>['a','b','c'],indexOf('a') -> 0
>['a','b','c'],indexOf('e') -> -1

To fix your issue 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]);
}

edited Sep 14, 2016 at 12:41

answered Sep 14, 2016 at 12:27

Nix

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3 Comments

James Beau Over a year ago

Thank you Nix, that helps. Can you tell me how I would search the letter array for a specific character?

Nix Over a year ago

You would want to use index of. ['a','b','c'],indexOf('a') would return the index if it finds it, if not it will return -1

Rajesh Dixit Over a year ago

@Nix you can move code of pushing in repeat in else block. This will ensure only unique values in repeat. Sample Fiddle

spankajd · Accepted Answer · 2016-09-14 12:54:22Z

0

try following code...

function duplicateEncode(word){

  var repeat = [];
  var result = [];
  var letters = word.split('');
  for (i=0; i < letters.length; i++){
      if (repeat.indexOf(letters[i]) != -1) {
          result.push(")");
      } else {
          result.push("(");
      }
      repeat.push(letters[i]);
   }
   return result;
 }

answered Sep 14, 2016 at 12:54

spankajd

9527 silver badges14 bronze badges

2 Comments

James Beau Over a year ago

Thank you, that fixes the problem.

spankajd Over a year ago

@JamesBeau Pleases mark it as correct option... thank you :)

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