CODEWITHSUNDEEP
javascript
Marko
Marko

Reputation: 93

Splice NOT removing certain characters

I'm working on some codewars problems and I came to this 'remove noise thing', I guess the point is to escape backslash \ and use replace method, which was easy. But I didn't want to use replace, instead I found myself in trouble trying to remove items with splice method.

Funny thing is, when I debug in Chrome dev tools, step by step I see items get removed, but console.log spits out certain characters($/·|ªl) problematic to remove, and at the end gets returned and join with those characters. Why is that?

function removeNoise(str) {
  var base = "%$&/#·@|º\ª";
  var arr = str.split('');

  for(var i = 0; i < arr.length; i++) {
    var item = arr[i];
    var condition = base.indexOf(item);
    if(condition + 1) {
      //works like a charm
      //arr[i] = '';

      arr.splice(i,1); 
      //this thing wont work
      //when debugging it removes the items from the array
      //console log print no removing
    }
  }
  return arr.join(''); 
}

removeNoise('he%$&/#·@|º\ª\llo'); //=> $/·|ªllo

Upvotes: 2

Views: 265

Answers (2)

phuzi
phuzi

Reputation: 13060

You're removing characters from your array. This will throw your indexer variable i out of sync with the characters you want to test. Easy way to fix is to start at the end of the array working your way to the beginning.

Change your for loop to this.

for(var i = arr.length -; i <= 0; i--) {


function removeNoise(str) {
  var base = "%$&/#·@|º\ª";
  var arr = str.split('');

  for(var i = arr.length - 1; i <= 0 ; i--) {
    var item = arr[i];
    if(base.indexOf(item) >= 0) {
      //remove the offending character
      arr.splice(i,1); 
    }
  }
  return arr.join(''); 
}

removeNoise('he%$&/#·@|º\ª\llo'); //=> $/·|ªllo

Upvotes: 2

T.J. Crowder
T.J. Crowder

Reputation: 1074485

You're using splice to remove entries from your array, but you're then incrementing i for the next loop. If you remove the entry at index 5 from a 10-entry array, what was the entry at index 6 is now at index 5 (of what's now a 9-entry array), so you don't want to increment your index.

The solution is to use a while loop and only update i if you don't splice:

function removeNoise(str) {
  var base = "%$&/#·@|º\ª";
  var arr = str.split('');

  var i = 0;
  while (i < arr.length) {
    var item = arr[i];
    var condition = base.indexOf(item);
    if (condition + 1) {
      // Remove this entry, reuse same value for 'i'
      arr.splice(i,1); 
    } else {
      // Don't remove this entry, move to next
      ++i;
    }
  }
  return arr.join(''); 
}

var result = removeNoise('he%$&/#·@|º\ª\llo');
var pre = document.createElement('pre');
pre.appendChild(
  document.createTextNode(result)
);
document.body.appendChild(pre);

Upvotes: 7

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