Returning multiple index values from an array using Javascript

Question

I have an array containing the individual letters of a word and i want to search the array to return the index values of certain letters. However, if the word contains more a letter more than once (such as 'tree') the programme only returns one index value.

This is a sample of the code:

var chosenWord = "tree";     
var individualLetters = chosenWord.split('');
var isLetterThere = individualLetters.indexOf(e);
console.log(isLetterThere);

this code will return the number '2', as that is the first instance of the letter 'e'. How would i get it to return 2 and 3 in the integer format, so that i could use them to replace items in another array using the .splice function.

Write a function to iterate over each letter, check, and tally up results. — tymeJV
– tymeJV, Commented Jan 21, 2015 at 21:41
How do you want the indexes returned: as text, as an array, etc.? — JRulle
– JRulle, Commented Jan 21, 2015 at 21:43
Hint: indexOf takes a second parameter, as the position where it should start searching from. developer.mozilla.org/de/docs/Web/JavaScript/Reference/… — C3roe
– C3roe, Commented Jan 21, 2015 at 21:50

C3roe · Accepted Answer · 2015-01-21 22:01:54Z

1

indexOf takes a second parameter, as the position where it should start searching from.

So my approach would be:

function findLetterPositions(text, letter) {
    var positions = new Array(),
        pos = -1;
    while ((pos = text.indexOf(letter, pos + 1)) != -1) {
        positions.push(pos);
    }
    return positions;
}

console.log(findLetterPositions("Some eerie eels in every ensemble.", "e"));

http://jsfiddle.net/h2s7hk1r/

answered Jan 21, 2015 at 22:01

C3roe

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Comments

brso05 · Accepted Answer · 2015-01-21 21:50:50Z

0

You could write a function like this:

function indexesOf(myWord, myLetter)
{
    var indexes = new Array();
    for(var i = 0; i < myWord.length; i++)
    {
        if(myWord.charAt(i) == myLetter)
        {
            indexes.push(i);
        }
    }
    return indexes;
}
console.log(indexesOf("tree", "e"));

answered Jan 21, 2015 at 21:50

brso05

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2 Comments

C3roe Over a year ago

I didn’t, but looping through every single character and comparing it yourself is rather inefficient – using already built-in functionality such as indexOf will likely perform better. (Not that is necessarily matters for typical use cases.)

Benjamin De Cock Over a year ago

That's actually not true: loops are faster than indexOf.

Mic · Accepted Answer · 2015-01-21 21:51:18Z

0

Loop through it as here:

var chosenWord = "tree";
var specifiedLetter = "e";
var individualLetters = chosenWord.split('');
var matches = [];
for(i = 0;i<individualLetters.length;i++){
  if(individualLetters[i] == specifiedLetter)
    matches[matches.length] = i; 
}

console.log(matches);

answered Jan 21, 2015 at 21:51

Mic

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Comments

Etheryte · Accepted Answer · 2015-01-21 21:54:56Z

0

An alternative using string methods.

var str = "thisisasimpleinput";
var cpy = str;
var indexes = [];
var n = -1;
for (var i = cpy.indexOf('i'); i > -1; i = cpy.indexOf('i')) {
  n += i;
  n++;
  indexes.push(n);
  cpy = cpy.slice(++i);
}
alert(indexes.toString());

answered Jan 21, 2015 at 21:54

Etheryte

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Comments

Benjamin De Cock · Accepted Answer · 2015-01-21 21:56:01Z

0

var getLetterIndexes = function(word, letter) {
  var indexes = [];
  word.split("").forEach(function(el, i) {
    el === letter && indexes.push(i);
  });
  return indexes;
};

getLetterIndexes("tree", "e"); // [2, 3]

answered Jan 21, 2015 at 21:56

Benjamin De Cock

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