JS string.split() without removing the delimiters

Question

How can I split a string without removing the delimiters?

Let's say I have a string: var string = "abcdeabcde";

When I do var newstring = string.split("d"), I get something like this:

["abc","eabc","e"]

But I want to get this:

["abc","d","eabc","d","e"]

When I tried to do my "split2" function, I got all entangled in splice() and indexes and "this" vs "that" and ... aargh! Help! :D

@ruffin It's not marked but has the same comment pointing back here. They are both *suggested* as duplicates of each other - we should somehow make up our minds which one to close :) — BartoszKP, Nov 26 '18 at 20:35

score 85 · Answer 1 · answered Dec 22 '10 at 22:16

85

Try:

"abcdeabcde".split(/(d)/);

answered Dec 22 '10 at 22:16

Kai

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Note this doesn't work in IE due to JScript bugs. – bobince Dec 22 '10 at 22:20
7

OP didn't specify if the environment was a browser or not – Kai Dec 22 '10 at 22:23
Which IE doesn't work? – CMCDragonkai Aug 29 '13 at 05:16
These are capturing parenthesis. They are the correct way to keep (part of) the separator strings in the returned array as odd entries. – AturSams May 18 '17 at 15:07
What if I want the result to be ["abc", "deabc", "de"] ? like having the splict character joined with the next split? – Mike Aono Jul 18 '17 at 10:12
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@MikeAono: https://stackoverflow.com/a/45323715/859877, by using regex `/(?=d)/g` – micha Jul 26 '17 at 10:09
4

This should be the accepted answer: it's simpler and safer, and IE is rarely a requirement lately – Nick McCurdy Sep 22 '19 at 18:29

score 41 · Answer 2 · answered Jul 26 '17 at 10:04

41

I like Kai's answer, but it's incomplete. Instead use:

"abcdeabcde".split(/(?=d)/g) //-> ["abc", "deabc", "de"]

This is using a Lookahead Zero-Length Assertion in regex, which makes a match not part of the capture group. No other tricks or workarounds needed.

answered Jul 26 '17 at 10:04

micha

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Is there a solution to get this result : //-> ["abcd", "eabcd", "e"] – forresst Sep 19 '19 at 08:39
@forresst Not with a single split command, AFAIK. But the accepted answer oddly enough does almost that, except with leading delimiters in stead of trailing. – Joachim Lous Oct 23 '19 at 13:37
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@forresst @JoachimLous You can just use a lookbehind approach, which is also described on the page linked by micha. E.g.: `"abcdeabcde".split(/(?<=d)/g)` – F Lekschas Jan 21 '22 at 21:37

score 37 · Accepted Answer · edited Apr 29 '13 at 12:45

37

Try this:

Replace all of the "d" instances into ",d"
Split by ","

var string = "abcdeabcde";
var newstringreplaced = string.replace(/d/gi, ",d");
var newstring = newstringreplaced.split(",");
return newstring;

Hope this helps.

edited Apr 29 '13 at 12:45

mplungjan

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answered Dec 22 '10 at 22:11

InfoLearner

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fastest answer according to firebugs profiler – Ege Özcan Dec 22 '10 at 22:15
5

Your solution has one mistake - it works when I replace the instances not with ",d", but with ",d,". Nice idea! Accepting because of the simplicity :) – Martin Janiczek Dec 22 '10 at 22:17
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"abcdeabcde".split(/(d)/); – Kai Dec 22 '10 at 22:19
38

Fails for any `,` in the original string. – bobince Dec 22 '10 at 22:23
bobince, yes, I guess it's not safe if the original string contains ',' somewhere. But I like principle. – Martin Janiczek Dec 22 '10 at 22:25
How would you do this if your split regex had more than one delimniator? eg `/[abc]/` – dwjohnston Jan 16 '14 at 03:52
@dwjohnston This is the wrong answer... You are supposed to use capturing parenthesis like in Kai's answer. – AturSams May 18 '17 at 15:06
this adds empty strings to the array if there are adjacent occurrences of the target char. `abcdda => [abc, d, '', d, a]`, is there a way to remove those (elegantly, without performing a 2nd loop)? – Daniel Lizik May 11 '22 at 02:16

score 21 · Answer 4 · answered Dec 22 '10 at 22:19

21

var parts= string.split('d');
for (var i= parts.length; i-->1;)
    parts.splice(i, 0, 'd');

(The reversed loop is necessary to avoid adding ds to parts of the list that have already had ds inserted.)

answered Dec 22 '10 at 22:19

bobince

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+1 much safer than accepted answer. – alex Sep 16 '11 at 01:39
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plus one for using ```-->``` operator :D – Mars Robertson Feb 21 '15 at 22:33
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[What is the name of the “-->” operator](http://stackoverflow.com/q/1642028/1529630) – Oriol Nov 14 '16 at 17:39
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This is better than the accepted answer, better than regexing or replacing with a special character that might naturally occur – Benjamin Intal May 06 '20 at 04:08
Seeing this answer, I'm once again happy to use [prettier](https://prettier.io/) … +1 for the functionality though! – panepeter Sep 20 '20 at 15:30

udn79 · Answer 5 · 2012-12-10T23:19:45.923

5

split - split is used to create separate lines not for searching.

[^d] - find a group of substrings not containing "d"

var str = "abcdeabcde";

str.match(/[^d]+|d/g)         // ["abc", "d", "eabc", "d", "e"]
or
str.match(/[^d]+/g)           // ["abc", "eabc", "e"]
or
str.match(/[^d]*/g)           // ["abc", "", "eabc", "", "e", ""]

Read "RegExp Object" if you do not want problems with the "javascript".

edited Dec 10 '12 at 23:19

answered Dec 10 '12 at 22:26

udn79

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No problem. I've tried make it a little clearer. Please feel free to rollback or edit if I've made a mistake. – Conrad Frix Dec 10 '12 at 23:06
Global objects change affects the speed. Methods "RegExp" - versatile and quick. If the code is large, it is easier to understand the code. This is my opinion. – udn79 Dec 10 '12 at 23:17

Ebrahim Byagowi · Answer 6 · 2013-07-04T13:56:23.100

This is my version for regexp delimiters. It has same interface with String.prototype.split; it will treat global and non global regexp with no difference. Returned value is an array that odd member of it are matched delimiters.

function split(text, regex) {
    var token, index, result = [];
    while (text !== '') {
        regex.lastIndex = 0;
        token = regex.exec(text);
        if (token === null) {
            break;
        }
        index = token.index;
        if (token[0].length === 0) {
            index = 1;
        }
        result.push(text.substr(0, index));
        result.push(token[0]);
        index = index + token[0].length;
        text = text.slice(index);
    }
    result.push(text);
    return result;
}

// Tests
assertEquals(split("abcdeabcde", /d/), ["abc", "d", "eabc", "d", "e"]);
assertEquals(split("abcdeabcde", /d/g), ["abc", "d", "eabc", "d", "e"]);
assertEquals(split("1.2,3...4,5", /[,\.]/), ["1", ".", "2", ",", "3", ".", "", ".", "", ".", "4", ",", "5"]);
assertEquals(split("1.2,3...4,5", /[,\.]+/), ["1", ".", "2", ",", "3", "...", "4", ",", "5"]);
assertEquals(split("1.2,3...4,5", /[,\.]*/), ["1", "", "", ".", "2", "", "", ",", "3", "", "", "...", "4", "", "", ",", "5", "", ""]);
assertEquals(split("1.2,3...4,5", /[,\.]/g), ["1", ".", "2", ",", "3", ".", "", ".", "", ".", "4", ",", "5"]);
assertEquals(split("1.2,3...4,5", /[,\.]+/g), ["1", ".", "2", ",", "3", "...", "4", ",", "5"]);
assertEquals(split("1.2,3...4,5", /[,\.]*/g), ["1", "", "", ".", "2", "", "", ",", "3", "", "", "...", "4", "", "", ",", "5", "", ""]);
assertEquals(split("1.2,3...4,5.", /[,\.]/), ["1", ".", "2", ",", "3", ".", "", ".", "", ".", "4", ",", "5", ".", ""]);
assertEquals(split("1.2,3...4,5.", /[,\.]+/), ["1", ".", "2", ",", "3", "...", "4", ",", "5", ".", ""]);
assertEquals(split("1.2,3...4,5.", /[,\.]*/), ["1", "", "", ".", "2", "", "", ",", "3", "", "", "...", "4", "", "", ",", "5", "", "", ".", ""]);
assertEquals(split("1.2,3...4,5.", /[,\.]/g), ["1", ".", "2", ",", "3", ".", "", ".", "", ".", "4", ",", "5", ".", ""]);
assertEquals(split("1.2,3...4,5.", /[,\.]+/g), ["1", ".", "2", ",", "3", "...", "4", ",", "5", ".", ""]);
assertEquals(split("1.2,3...4,5.", /[,\.]*/g), ["1", "", "", ".", "2", "", "", ",", "3", "", "", "...", "4", "", "", ",", "5", "", "", ".", ""]);

// quick and dirty assert check
function assertEquals(actual, expected) {
  console.log(JSON.stringify(actual) === JSON.stringify(expected));
}

score 2 · Answer 7 · answered Dec 22 '10 at 22:12

Try this:

var string = "abcdeabcde";
    var delim = "d";
    var newstring = string.split(delim);
    var newArr = [];
    var len=newstring.length;
    for(i=0; i<len;i++)
    {
        newArr.push(newstring[i]);
        if(i != len-1)newArr.push(delim);
    }

score 0 · Answer 8 · answered Dec 22 '10 at 22:16

0

function split2(original){
   var delimiter = "d", result = [], tmp;
   tmp = original.split(delimiter);
   tmp.forEach(function(x){result.push(x); result.push(delimiter); });
   return result;
}

answered Dec 22 '10 at 22:16

pc1oad1etter

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heesu Suh · Answer 9 · 2017-07-28T14:38:44.377

0

Try this

"abcdeabcde".split("d").reduce((result, value, index) => {
    return (index !== 0) ? result.concat(["d", value]) : result.concat(value)
}, [])

edited Jul 28 '17 at 14:38

answered Jul 28 '17 at 13:35

heesu Suh

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score -1 · Answer 10 · answered Dec 22 '10 at 22:19

-1

Try this

var string = "abcdeabcde";
var res = string.replace( /d/g, 'd\0' ).split(/(?=d)|\0/);
console.log( res );
//["abc", "d", "eabc", "d", "e"]

answered Dec 22 '10 at 22:19

meouw

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JS string.split() without removing the delimiters

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