Split string into sentences in javascript

Question

Currently i am working on an application that splits a long column into short ones. For that i split the entire text into words, but at the moment my regex splits numbers to

Answer 1

Use lookahead to avoid replacing dot if not followed by space + word char:

sentences = str.replace(/(?=\s*\w)\./g,'.|').replace(/\?/g,'?|').replace(/\!/g,'!|').split("|");

OUTPUT:

["This is a long string with some numbers [125.000,55 and 140.000] and an end. This is another sentence."]

Answer 2

you forgot to put '\s' in your regexp.

try this one

var str = "This is a long string with some numbers [125.000,55 and 140.000] and an end. This is another sentence.";
var sentences = str.replace(/\.\s+/g,'.|').replace(/\?\s/g,'?|').replace(/\!\s/g,'!|').split("|");
console.log(sentences[0]);
console.log(sentences[1]);

http://jsfiddle.net/hrRrW/

Answer 3

str.replace(/([.?!])\s*(?=[A-Z])/g, "$1|").split("|")

Output:

[ 'This is a long string with some numbers [125.000,55 and 140.000] and an end.',
  'This is another sentence.' ]

Breakdown:

([.?!]) = Capture either . or ? or !

\s* = Capture 0 or more whitespace characters following the previous token ([.?!]). This accounts for spaces following a punctuation mark which matches the English language grammar.

(?=[A-Z]) = The previous tokens only match if the next character is within the range A-Z (capital A to capital Z). Most English language sentences start with a capital letter. None of the previous regexes take this into account.

---

The replace operation uses:

"$1|"

We used one "capturing group" ([.?!]) and we capture one of those characters, and replace it with $1 (the match) plus |. So if we captured ? then the replacement would be ?|.

Finally, we split the pipes | and get our result.

---

So, essentially, what we are saying is this:

1) Find punctuation marks (one of . or ? or !) and capture them

2) Punctuation marks can optionally include spaces after them.

3) After a punctuation mark, I expect a capital letter.

Unlike the previous regular expressions provided, this would properly match the English language grammar.

From there:

4) We replace the captured punctuation marks by appending a pipe |

5) We split the pipes to create an array of sentences.

Answer 4

You're safer using lookahead to make sure what follows after the dot is not a digit.

var str ="This is a long string with some numbers [125.000,55 and 140.000] and an end. This is another sentence."

var sentences = str.replace(/\.(?!\d)/g,'.|');
console.log(sentences);

If you want to be even safer you could check if what is behind is a digit as well, but since JS doesn't support lookbehind, you need to capture the previous character and use it in the replace string.

var str ="This is another sentence.1 is a good number"

var sentences = str.replace(/\.(?!\d)|([^\d])\.(?=\d)/g,'$1.|');
console.log(sentences);

An even simpler solution is to escape the dots inside numbers (replace them with $$$$ for example), do the split and afterwards unescape the dots.

Answer 5

str.replace(/(\.+|\:|\!|\?)(\"*|\'*|\)*|}*|]*)(\s|\n|\r|\r\n)/gm, "$1$2|").split("|")

The RegExp (see on Debuggex):

• (.+|:|!|\?) = The sentence can end not only by ".", "!" or "?", but also by "..." or ":"
• (\"|\'|)*|}|]) = The sentence can be surrounded by quatation marks or parenthesis
• (\s|\n|\r|\r\n) = After a sentense have to be a space or end of line
• g = global
• m = multiline

Remarks:

• If you use (?=[A-Z]), the the RegExp will not work correctly in some languages. E.g. "Ü", "Č" or "Á" will not be recognised.

Answer 6

@Roger Poon and @Antonín Slejška 's answers work good.

It'd better if we add trim function and filter empty string:

const splitBySentence = (str) => {
  return str.replace(/([.?!])(\s)*(?=[A-Z])/g, "$1|")
    .split("|")
    .filter(sentence => !!sentence)
    .map(sentence => sentence.trim());
}

const splitBySentence = (str) => {
  return str.replace(/([.?!])(\s)*(?=[A-Z])/g, "$1|").split("|").filter(sentence => !!sentence).map(sentence => sentence.trim());
}

const content = `
The Times has identified the following reporting anomalies or methodology changes in the data for New York:

May 6: New York State added many deaths from unspecified days after reconciling data from nursing homes and other care facilities.

June 30: New York City released deaths from earlier periods but did not specify when they were from.

Aug. 6: Our database changed to record deaths by New York City residents instead of deaths that took place in New York City.

Aug. 20: New York City removed four previously reported deaths after reviewing records. The state reported four new deaths in other counties.(extracted from NY Times)
`;

console.log(splitBySentence(content));