Need to filter out repeating consecutive characters in a string using JavaScript

Question

It is one of the challenges in Codewars, and I am supposed to write a function that will take a string and return an array, in which I can't have two consecutive identical elements. Also, the order should not change.

For example, if I pass a string "hhhhheeeelllloooooohhheeeyyy", then the function should return an array = ["h","e","l","o","h","e","y"].

This is my code.

    var uniqueInOrder=function(iterable){
  //your code here - remember iterable can be a string or an array
     var unique = [];
   for( var i = 0; i < iterable.length; i++) {
      unique.push(iterable[i]);
   } 

   for( var j = 0, k = 1; j < unique.length; j++, k = j + 1 ){
      if(unique[j] === unique[k]){
         unique.splice(k,1);
     }
    }
   return unique;
 }

so, if I pass a string, such as "hhhhheeeeeellllloooo",it doesn't work as I intend it to because the value of j keeps incrementing, hence I can't filter out all the identical elements.

I tried tweaking the logic, such that whenever the unique[j] === unique[k] the value of j would become zero, and if that's not the case, then things would continue as they are supposed to do.

This got me an infinite loop.

I need your help.

Try only working with one copy of the data. Trying to compare two copies and keeping their indices straight is overcomplicating the issue. All you need to track is the current value and either the next or previous value. If current value equals either of those, then discard one because it's a duplicate. As an alternative, you could look into regular expressions. They can do this type of replacement in one line, and if you start using regular expressions now, you'll find uses for them forever. — LinuxDisciple
– LinuxDisciple, Commented Oct 7, 2016 at 3:58
@LinuxDisciple Hi, the idea of tracking the next or previous value came to mind, but I can't come up with a code for that. I'll try it a few more times, and if I still don't get it, then I'll reach out to you. Thank You. — relentless-coder
– relentless-coder, Commented Oct 7, 2016 at 4:07

relentless-coder · Accepted Answer · 2016-10-07 04:19:41Z

1

The second for loop is fail because unique.length is not constant during the run. I think your problem can be solved like this:

var temp = iterable[0];
unique.push(iterable[0]);
for( var i = 1; i < iterable.length; i++) {
   if(iterable[i] != temp) {
       unique.push(iterable[i]);
       temp = iterable[i];
   }
}

Hope it helps!

edited Oct 7, 2016 at 4:19

relentless-coder

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answered Oct 7, 2016 at 4:06

KAngel7

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7 Comments

LinuxDisciple Over a year ago

If the first character is unique, how does it get into unique? i is never 0...

KAngel7 Over a year ago

you are right! so lets fix by add the first temp to unique array I think?

LinuxDisciple Over a year ago

That would work, but then isn't temp always equal to the last value in unique? Do we need temp at all?

Rohith K N Over a year ago

for loop will not fail because unique.length is dynamic, i.e will change with addition of new elements to array.

relentless-coder Over a year ago

Yes, that. I added an extra line of code, that would unique.push(iterable[0]) before the for loop.

|

Angrysheep · Accepted Answer · 2016-10-07 03:59:20Z

1

You only need to compare the current index of iterable against the last character in unique:

function(iterable){
  var unique = []

  for(var i=0; i< iterable.length; i++){
    if(unique.length < 1){
      unique.push(iterable[i])
    } else if(iterable[i] !== unique[unique.length - 1]) {
      unique.push(iterable[i])
    }
  }

  return unique
}

answered Oct 7, 2016 at 3:59

Angrysheep

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Comments

Rohith K N · Accepted Answer · 2016-10-07 04:11:01Z

0

I think this will help you:

var word="hhhhheeeelllloooooohhheeeyyy"
function doit(iterable){
  var unique = []
  unique[0]=iterable[0]
  for(var i=1; i< iterable.length; i++){
     if(iterable[i] !== unique[unique.length - 1]) {
      unique.push(iterable[i])
    }
  }
  return unique
}
alert(doit(word))

for loop will not fail because unique.length is dynamic, i.e will change with addition of new elements to array.

Tested in Internet Explorer too. Here is the link to jsfiddle: https://jsfiddle.net/kannanore/z5gbee55/

answered Oct 7, 2016 at 4:11

Rohith K N

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1 Comment

relentless-coder Over a year ago

I edited @K.Angel7 answer. Added, unique.push(iterable[0]).

DragoRaptor · Accepted Answer · 2016-10-07 04:23:10Z

0

var str = "hhhhheeeelllloooooohhheeeyyy";
var strLen = str.length;
var newStr = "";
for(var i=0; i < strLen; i++ ){
    var chr$ = str.charAt(i);  
    //if(i==0) {newStr = chr$ };
    if(chr$ == str.charAt(i+1)){
        strLen = str.length;`enter code here`
    }else{
        newStr = newStr + chr$ ;
    }
}
//document.write(newStr);
console.log(newStr);
//Answer: helohey

answered Oct 7, 2016 at 4:23

DragoRaptor

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1 Comment

relentless-coder Over a year ago

I am supposed to return an array. Although, I've got the correct solution, but I thought I should point it out.

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