Writing a string splitting function without using the split method in javascript

Question

I'm trying to create a simple function that takes a string and a delimiter and then splits the string into an array based on the delimiter value. I'm trying to write this function without using the split method in javascript. So say I have a sampleInput = '123$456$789' and a delimiter = '$' then the function stringDelimiter(sampleInput, delimiter) will return ['123', '456', '789'].

    var stringDelimiter = function (sampleInput, delimiter) {

        var stringArray = [];
        var garbageArray = [];
        var j = 0;


        for (var i = 0; i < sampleInput.length; i++) {

            if (sampleInput.charAt(i) == delimiter) {
                garbageArray = sampleInput.charAt(i);
                j++;
            } else {
            if (!stringArray[j]) stringArray[j] = '';
            stringArray[j] += sampleInput.charAt(i);
            }
        }
        return stringArray;
    }

The problem I'm having is if the delimiter appears at the beginning of the string it returns the first element of the array undefined. I'm stuck as to how I can handle this case. So if I have sampleInput = '$123$456$789' and delimiter = '$' it returns ['123', '456', '789'] and not ['undefined','123', '456', '789']. Any help would be appreciated.

Generally, if there's a built-in function you can use, you may as well use it. Since split() is pretty well supported everywhere, I see few reasons you shouldn't use it. — ArtOfCode
– ArtOfCode, Commented Jul 15, 2014 at 18:40
This is probably for a school assignment where reinventing the wheel is common. — Zach M.
– Zach M., Commented Jul 15, 2014 at 18:42
FWIW, the behaviour of the real split function would be to return an empty string in the first element of the result, not an undefined value. — Alnitak
– Alnitak, Commented Jul 15, 2014 at 18:43
Also, consider using indexOf() to directly find the index of the next delimiter, and substr to extract from the current position to there. — Alnitak
– Alnitak, Commented Jul 15, 2014 at 18:45

Scott Sauyet · Accepted Answer · 2014-07-15 19:20:35Z

5

This is a little simpler, and it might do what you want:

var stringDelimiter = function (sampleInput, delimiter) {
    var stringArray = [''];
    var j = 0;

    for (var i = 0; i < sampleInput.length; i++) {
        if (sampleInput.charAt(i) == delimiter) {
            j++;
            stringArray.push('');
        } else {
            stringArray[j] += sampleInput.charAt(i);
        }
    }
    return stringArray;
}

Your garbageArray seemed unnecessary.

edited Jul 15, 2014 at 19:20

answered Jul 15, 2014 at 19:09

Scott Sauyet

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Comments

Scott Sauyet · Accepted Answer · 2014-07-15 20:11:11Z

1

What about using regular expressions?

function x_split(s)
{
     return s.match(/([^$]+)/g);
}

E.g. http://jsfiddle.net/2F9MX/2/

edited Jul 15, 2014 at 20:11

Scott Sauyet

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answered Jul 15, 2014 at 19:14

Bill

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5 Comments

Scott Sauyet Over a year ago

The title includes "without using the split method". I don't know why this is a requirement, possibly homework, but it's part of the specification here.

Bill Over a year ago

How is using match using the split method?

Scott Sauyet Over a year ago

Total misread. I apologize. I saw the split in the function name and read it as part of the body. Sorry.

Scott Sauyet Over a year ago

There are two flaws I see: First, the OP wanted the delimiter to be a parameter. Second, this has the same problem that it doesn't match the String.prototype.split behavior when the delimiter comes first (or last either.)

Bill Over a year ago

Check the fiddle, it does what s/he says it should do, that "$123$456$789" should return ['123', '456', '789'] and not ['undefined','123', '456', '789']. Adding the delimiter as a second parameter is left as an exercise for the reader ;-).

Nikhil Baliga · Accepted Answer · 2014-07-15 18:40:31Z

0

If the current character is delimiter and if the current iteration is 0, continue

answered Jul 15, 2014 at 18:40

Nikhil Baliga

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Comments

Zoltán Tamási · Accepted Answer · 2014-07-15 19:12:29Z

0

This function accepts a string, a delimiter and a flag if empty (aka undefined, null or empty string) elements should be removed from the result array. (Not tested, it was a quick code for now.)

UPDATE

Now it's tested (a bit) and corrected, and I've created a jsFiddle here. Besides, it supports empty delimiter, empty input string, and delimiter with length > 1.

function CustomSplit(str, delimiter, removeEmptyItems) {
  if (!delimiter || delimiter.length === 0) return [str];
  if (!str || str.length === 0) return [];
  var result = [];
  var j = 0;
  var lastStart = 0;
  for (var i=0;i<=str.length;) {
    if (i == str.length || str.substr(i,delimiter.length) == delimiter)
    {
      if (!removeEmptyItems || lastStart != i)
      {
          result[j++] = str.substr(lastStart, i-lastStart);
      }
      lastStart = i+delimiter.length;
      i += delimiter.length;    
    } else i++;
  }
  return result;
}

edited Jul 15, 2014 at 19:12

answered Jul 15, 2014 at 18:44

Zoltán Tamási

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3 Comments

Alnitak Over a year ago

fail's the OP's requirement not to use split itself.

megawac Over a year ago

!delimiter || delimiter.length === 0 is redundant. !"" is true

Zoltán Tamási Over a year ago

@megawac You're right, but those lines are just coming for me by instincts, rather longer check than forgotten check. (I used to do a similar check for expected arrays as well, and there it's not redundant if you want to include empty arrays in the condition.)

Artur Barseghyan · Accepted Answer · 2019-05-07 13:57:01Z

0

In case someone needs one for TypeScript (and MicroBit for which I wrote it), here's a altered version of @Scott Sauyet answer for TypeScript:

The code:

function splitString(sampleInput: string, delimiter: string): string[] {
    let stringArray = ['']
    let j = 0

    for (let i = 0; i < sampleInput.length; i++) {
        if (sampleInput.charAt(i) == delimiter) {
            j++;
            stringArray.push('')
        } else {
            stringArray[j] += sampleInput.charAt(i)
        }
    }
    return stringArray
}

Usage example

let myString = "Lorem ipsum dolor sit amet"
let myArray = splitString(myString, " ")
myArray[0]  // "Lorem"
myArray[1]  // "ipsum"

answered May 7, 2019 at 13:57

Artur Barseghyan

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3 Comments

hannad rehman Over a year ago

splitString('hello world','hello') fails

Artur Barseghyan Over a year ago

It's because delimiter is supposed to be a single character, not a word.

hannad rehman Over a year ago

would be nice to support any number of chars.

Awais Ibrar · Accepted Answer · 2022-01-04 10:56:12Z

0

You can use this method

const splitCode = (strValue, space) => {
let outPutArray = [];
let temp = '';
for(let i= 0; i< strValue.length; i++){
  let temp2 = '';
  for(let j= i; j<space.length+i;j++){
    temp2 = temp2+strValue[j];
  }
 if(temp2 === space){
    outPutArray.push(temp);
    i=i+space.length-1;
    temp = '';
  }else{
     temp = temp+strValue[i];
 }
}
return outPutArray.concat(temp)
}

answered Jan 4, 2022 at 10:56

Awais Ibrar

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