CODEWITHSUNDEEP
javascriptindexof
slurrr
slurrr

Reputation: 2764

Trouble Using indexOf While Looping Through a Word Checking for Matching Letters

Please help me think this through... I am trying to check and see if all of the letters in the second element of an array are contained within the letters of the first element, ignoring case. So "Aliens" and "lines" should return true because all of the letters in "lines" are included in "Aliens" even though they are not in order. My problem is when I try to loop through the first element my code appears to only be checking the first letter for a match and not continuing through the entire word.

function mutation(arr) {
  var firstElement = arr[0].toLowerCase().split('');
  var secondElement = arr[1].toLowerCase().split('');
  for (var i = 0; i < firstElement.length; i++) {
    return firstElement.indexOf(secondElement[i]) != -1;
  }
}
mutation(["hello", "neo"]);

Any ideas?

Upvotes: 1

Views: 556

Answers (5)

Paul Kienitz
Paul Kienitz

Reputation: 878

Don't split the first element -- treat it as a string and use the indexOf method on that with the single characters from the second element.

Update -- yes, like Depperm's code below, but throw a toLowerCase on firstElement.

Upvotes: 0

Prateek Jain
Prateek Jain

Reputation: 1552

it's checking only for the first letter because as it enters into the loop, the return statement gets executed, and hence the function terminates.

function mutation(arr) {
  var firstElement = arr[0];
  var secondElement = arr[1];
  return secondElement.split('').every(function(elem) {return  firstElement.indexOf(elem) != -1;} );
}
mutation(["Aliens", "lines"]);

Upvotes: 1

Daniel Rosano
Daniel Rosano

Reputation: 695

You can use map and reduce in order to save lines of code

function mutation(arr) {
  var secondElement = arr[1].toLowerCase().split('');
  var map = secondElement.map(function(a){return arr[0].indexOf(a) != -1});
  return map.reduce(function(a,b) {return a&&b;}, true);
}

On second line you check if each letter from second word is in first word (and save true/false). Third line just accumulate those results into a final variable

Reference https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_objects/Array/reduce https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_objects/Array/map

Upvotes: 1

Ben Griffiths
Ben Griffiths

Reputation: 1696

There are two issues with the function:

Firstly, it is returning after checking only the first letter, as you say.

Secondly, you need to use the length of the second element as your loop termination condition, since that's the one whose letters you are intending to loop through.

You need something more like this:

function mutation(arr) {
  var firstElement = arr[0].toLowerCase().split('');
  var secondElement = arr[1].toLowerCase().split('');
  for (var i = 0; i < secondElement.length; i++) {
     if(firstElement.indexOf(secondElement[i]) === -1) {
         return true;
     }
  }
  return false;
}

You might also want to handle some obvious boundary cases, like null/undefined/empty strings, but I've left that out for clarity.

Upvotes: 1

depperm
depperm

Reputation: 10756

Using what Paul Kienitz mentioned, also change your loop to loop through the second element to check each character in the first element to see if it finds that character in the first element. 

function mutation(arr) {
  var firstElement = arr[0];
  var secondElement = arr[1].toLowerCase().split('');
  var match=true;
  var temp;
  for (var i = 0; i < secondElement.length; i++) {
    temp = firstElement.indexOf(secondElement[i]);
    if(temp==-1)
      match=false;
  }
  return match;
}
mutation(["hello", "neo"]);

Upvotes: 0

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