How to count the number of lines of a string in javascript

Question

I would like to count the number of lines in a string. I tried to use this stackoverflow answer,

lines = str.split("\r\n|\r|\n"); 
return  lines.length;

on this string (which was originally a buffer):

 GET / HTTP/1.1
 Host: localhost:8888
 Connection: keep-alive
 Cache-Control: max-age=0
 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_2) AppleWebKit/535.2 (KHTML,like Gecko) Chrome/15.0.874.121 Safari/535.2
 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
 Accept-Encoding: gzip,deflate,sdch
 Accept-Language: en-US,en;q=0.8
 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3

and, for some reason, I got lines='1'.

Any idea how to make it work?

@BookOfZeus "\n" and "\r" are handled by his regexp. "\n\r" is plain wrong. — bezmax
– bezmax, Commented Dec 13, 2011 at 11:54
I've answered a related question, "What's the fastest way to test for a minimum number of lines or tokens?" stackoverflow.com/questions/39554154/… — Joe Lapp
– Joe Lapp, Commented Sep 18, 2016 at 4:38
@SupremeDolphin No it is not, at least not for the example given. See en.wikipedia.org/wiki/… : "The request line and other header fields must each end with <CR><LF>", that is \r\n. — bezmax
– bezmax, Commented Oct 15, 2019 at 13:39

Pavan · Accepted Answer · 2014-02-26 12:51:38Z

197

Using a regular expression you can count the number of lines as

 str.split(/\r\n|\r|\n/).length

Alternately you can try split method as below.

var lines = $("#ptest").val().split("\n");  
alert(lines.length);

working solution: http://jsfiddle.net/C8CaX/

edited Feb 26, 2014 at 12:51

answered Dec 13, 2011 at 11:54

Pavan

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6 Comments

SimplGy Over a year ago

Fails for this test case: 'Roomy Below:\n\nStart again.'. It detects 3 lines, when, visually, there are 4. This is because the split merges both new lines together.

Jools Over a year ago

@SimplGy What? It doesn't fail. It detects 3 lines because there are 3 lines, even visually. console.log('Roomy Below:\n\nStart again.') gives you 3 lines. If split merged new lines, this wouldn't work: console.log('Roomy Below:\n\nStart again.'.split('\n').join('\n')), but it does and you get the same 3 lines again.

SimplGy Over a year ago

You're right Jools, I messed up this re-creation case because visually that is 3 lines (the first \n ends a text line and the second one creates a blank line). I'm sure my objection was based on a real life scenario at some point but I have no idea what at this point.

Константин Ван Over a year ago

If your text only takes '\n' for new-line characters(e.g. a <textarea>'s value), you can consider using TEXT.match(/^/mg).length.

scenia Over a year ago

@Khamidulla You miscounted, "\n\n" has 3 lines, each containing an empty string. Every string (even the empty string) has 1 line, then each \n adds another line. It's really the same thing as looking at "1\n2\n3", which is the numbers 1, 2 and 3, each on their own line.

|

SL5net · Accepted Answer · 2023-03-14 11:57:46Z

84

Another short, potentially more performant than split, solution is:

const lines = (str.match(/\n/g) || '').length + 1

to avoid possible errors, it can help to convert it explicitly into a string ( https://stackoverflow.com/a/5196710/2891692 ) :

const lines = (String(str).match(/\n/g) || '').length + 1

edited Mar 14, 2023 at 11:57

SL5net

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answered May 6, 2017 at 12:46

ngryman

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6 Comments

asmmahmud Over a year ago

this is way better solution

Samuel Kirschner Over a year ago

like this solution, small improvement: the \r? isn't actually doing anything, (str.match(/\n/g) || '').length produces the same result, doesn't it?

hashed_name Over a year ago

Better solution, as split function creates new array which is heavy than this solution.

Bruno Desprez Over a year ago

both methods create a new array … str.match return an Array so does the split too … The split method return an Array of strings, but str.match return an Array of objects. I think an object take more space in memory than string …

TWiStErRob Over a year ago

@milahu for me split performs better :) it's surprising how bad for loop is.

|

David Hedlund · Accepted Answer · 2011-12-13 11:56:26Z

11

To split using a regex use /.../

lines = str.split(/\r\n|\r|\n/);

answered Dec 13, 2011 at 11:56

David Hedlund

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1 Comment

Alex Yu Over a year ago

Same rule but quite shorter /\r?\n/

Aadit M Shah · Accepted Answer · 2013-12-12 02:06:23Z

11

Hmm yeah... what you're doing is absolutely wrong. When you say str.split("\r\n|\r|\n") it will try to find the exact string "\r\n|\r|\n". That's where you're wrong. There's no such occurance in the whole string. What you really want is what David Hedlund suggested:

lines = str.split(/\r\n|\r|\n/);
return lines.length;

The reason is that the split method doesn't convert strings into regular expressions in JavaScript. If you want to use a regexp, use a regexp.

edited Dec 12, 2013 at 2:06

answered Dec 13, 2011 at 12:01

Aadit M Shah

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Comments

aleclarson · Accepted Answer · 2018-05-26 23:17:41Z

8

I made a performance test comparing split with regex, with a string and doing it with a for loop.

It seems that the for loop is the fastest.

NOTE: this code 'as is' is not useful for windows nor macos endline, but should be ok to compare performance.

Split with string:

split('\n').length;

Split with regex:

split(/\n/).length;

Split using for:

var length = 0;
for(var i = 0; i < sixteen.length; ++i)
  if(sixteen[i] == s)
    length++;

http://jsperf.com/counting-newlines/2

edited May 26, 2018 at 23:17

aleclarson

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answered Apr 13, 2015 at 14:26

jperelli

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1 Comment

milahu Over a year ago

funny, my benchmark says that for-loop is slowest

alexn · Accepted Answer · 2016-10-21 09:04:17Z

3

There are three options:

Using jQuery (download from jQuery website) - jquery.com

var lines = $("#ptest").val().split("\n");
return lines.length;

Using Regex

var lines = str.split(/\r\n|\r|\n/);
return lines.length;

Or, a recreation of a for each loop

var length = 0;
for(var i = 0; i < str.length; ++i){
    if(str[i] == '\n') {
        length++;
    }
}
return length;

edited Oct 21, 2016 at 9:04

alexn

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answered Dec 12, 2013 at 18:15

Joe

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1 Comment

Chris - Jr Over a year ago

This is not a true comment. There are not just three options.

hashed_name · Accepted Answer · 2019-05-13 06:57:39Z

2

Better solution, as str.split("\n") function creates new array of strings split by "\n" which is heavier than str.match(/\n\g). str.match(/\n\g) creates array of matching elements only. Which is "\n" in our case.

var totalLines = (str.match(/\n/g) || '').length + 1;

answered May 13, 2019 at 6:57

hashed_name

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Comments

Sandeep G B · Accepted Answer · 2011-12-13 11:56:22Z

1

Here is the working sample fiddle

Just remove additional \r\n and "|" from your reg ex.

answered Dec 13, 2011 at 11:56

Sandeep G B

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Comments

Krishna Jangid · Accepted Answer · 2019-08-05 11:10:31Z

1

 <script type="text/javascript">
      var multilinestr = `
        line 1
        line 2
        line 3
        line 4
        line 5
        line 6`;
      totallines = multilinestr.split("\n");
lines = str.split("\n"); 
console.log(lines.length);
</script>

thats works in my case

answered Aug 5, 2019 at 11:10

Krishna Jangid

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Comments

Chris - Jr · Accepted Answer · 2021-02-10 19:01:48Z

1

I was testing out the speed of the functions, and I found consistently that this solution that I had written was much faster than matching. We check the new length of the string as compared to the previous length.

const lines = str.length - str.replace(/\n/g, "").length+1;

let str = `Line1
Line2
Line3`;
console.time("LinesTimer")
console.log("Lines: ",str.length - str.replace(/\n/g, "").length+1);
console.timeEnd("LinesTimer")

answered Feb 10, 2021 at 19:01

Chris - Jr

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Comments

John Freeman · Accepted Answer · 2024-04-12 16:08:40Z

I've combined a few of the other answers into a performance test at https://jsperf.app/lenavi/4:

.match(/\n/g) from @ngryman and @hashed_name:

(text.match(/\n/g) || '').length + 1

.reduce(...) from @gil.fernandes:

[...text].reduce((a, c) => a + (c === '\n'), 1)

.split(/\r\n|\r|\n/) from @Joe, @Pavan, @Aadit M Shah, and @David Hedlund:

text.split(/\r\n|\r|\n/).length

.split(/\n/) for when you know the line ending, by @jperelli:

text.split(/\n/).length

.split('\n') which is the same as above, but using a string instead of a regex, by @Krishna Jangid, @jperelli, @Joe, and @Pavan:

text.split('\n').length

Here are the results on my machine with Chrome 123.0.6312.105:

.split('\n') is the fastest by far.
.split(/\n/) and .match(/\n/g) are virtually tied for second at 59% slower.
.split(/\r\n|\r|\n/) is about 87% slower.
.reduce(...) is 99% slower. Not even in the same ballpark.

The results are different (on my machine) with Firefox 123.0.1:

.split(/\n/) and .match(/\n/g) are virtually tied for first. I'm a little surprised that .split() did this well. Perhaps the SpiderMonkey JavaScript engine is special-casing this particular call.
.split('\n') is ~50% slower. I'm very surprised by the difference here between using a one-character string and a one-character regex.
.split(/\r\n|\r|\n/) is about 66% slower, or 1/3 the speed, which makes sense because it is doing up to 3x the comparisons.
.reduce(...) is 99% slower (again).

Node uses the same JavaScript engine (V8) as Chrome.

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