Split string at every nth linebreak using javascript

Question

I'm looking for a solution to split a string at every nth linebreak. Lets say i have one string that has six lines

"One\nTwo\nThree\nFour\nFive\nSix\n"

So splitting at 3rd line break would give me something like

"One\nTwo\nThree\n" and "Four\nFive\nSix\n"

I've found solutions to do it at nth character, but i can't be definite of at what character length the nth break would occur. I hope my question is clear. Thanks.

@CasimiretHippolyte Not quite sure how to do that, i've found patterns that match multiple lines, having trouble finding patterns that match every n number of lines. — Haider Ali
– Haider Ali, Commented Sep 29, 2017 at 17:52
@HaiderAli In this case, How do you want your output to be when your input is One\n\n\n\n\nTwo\n\nThree\n\nFour\n\nFive\n\n\n\nSix\n? — Gurmanjot Singh
– Gurmanjot Singh, Commented Sep 29, 2017 at 18:03
@Gurman That will not occur, the string is programatically prepared from an array. I'd rather split a string rather paginate an array ;p — Haider Ali
– Haider Ali, Commented Sep 29, 2017 at 18:12

Casimir et Hippolyte · Accepted Answer · 2017-09-29 19:23:47Z

4

Instead of using the String.prototype.split, it's easier to use the String.prototype.match method:

"One\nTwo\nThree\nFour\nFive\nSix\n".match(/(?=[\s\S])(?:.*\n?){1,3}/g);

demo

pattern details:

(?=[\s\S]) # ensure there's at least one character (avoid a last empty match)

(?:.*\n?)  # a line (note that the newline is optional to allow the last line)

{1,3} # greedy quantifier between 1 and 3
      # (useful if the number of lines isn't a multiple of 3)

Other way with Array.prototype.reduce:

"One\nTwo\nThree\nFour\nFive\nSix\n".split(/^/m).reduce((a, c, i) => {
    i%3  ?  a[a.length - 1] += c  :  a.push(c);
    return a;
}, []);

edited Sep 29, 2017 at 19:23

answered Sep 29, 2017 at 17:53

Casimir et Hippolyte

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Jan · Accepted Answer · 2017-09-29 18:00:21Z

2

Straight-forward:

(?:.+\n?){3}

See a demo on regex101.com.

Broken down, this says:

(?:  # open non-capturing group
.+   # the whole line
\n?  # a newline character, eventually but greedy
){3} # repeat the group three times

edited Sep 29, 2017 at 18:00

answered Sep 29, 2017 at 17:52

Jan

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