javascript split string with multiple delimeters and expressions

Question

I have the following expression:

where('publishedDate').gte(new Date('2015-08-21T20:37:45.176Z')).sort({ field: 'asc', test: -1 });

that I would like to parse into the following tokens using javascript's string::split(regex):

where
('publishedDate')
gte
(new Date('2015-08-21T20:37:45.176Z'))
sort
({ field: 'asc', test: -1 })

but I'm having a hard time coming up with a suitable expression that does it. Any help is greatly appreciated!

You won't be able to use JS's regexes to parse text containing nested braces, because they have no suitable mechanism for this. This would be possible with, for instance PCRE's recursive regexes or .NET's balancing groups, but JS has no such feature. Write a tokenizer by hand, it's not complicated at all. — Lucas Trzesniewski
– Lucas Trzesniewski, Commented Aug 19, 2015 at 22:34
A regex impossibility? Hard to believe:-) I'll take a second or third opinion and if that also suggests it can't be done then I'll find a different approach. Thanks! — webteckie
– webteckie, Commented Aug 19, 2015 at 22:39
@webteckie: JavaScript's regular expressions are relatively weak compared with PCRE and such. (And this from a JavaScript fanboi.) Lucas is quite right about not having a means of handling abitrarily nested things (like the parens in your example). Regular expressions can be part of the solution, but not the entire solution. — T.J. Crowder
– T.J. Crowder, Commented Aug 19, 2015 at 22:47
@webteckie don't get me wrong - because you can do it with non-regular PCRE "regexes" for sure (I just showed a dirty example here). Just don't expect to be able to do the same thing with JS's braindead regexes ;) — Lucas Trzesniewski
– Lucas Trzesniewski, Commented Aug 19, 2015 at 22:49

manji · Accepted Answer · 2015-08-20 21:50:16Z

2

You can use this one:

/(\w+)(\(.+?\)(?=\.|;|$))/g

It works well on your input.

Demo: https://regex101.com/r/kV9lS4/1

How to get the matching tokens only:

var re = /(\w+)(\(.+?\)(?=\.|;))/g,
    str = "where('publishedDate').gte(new Date('2015-08-21T20:37:45.176Z'))" +
          ".sort({ field: 'asc', test: -1 });",
    result = [],
    arr;

while(arr = re.exec(str)) {
  result.push(arr[1]);
  result.push(arr[2]);
}

var re = /(\w+)(\(.+?\)(?=\.|;))/g,
    str = "where('publishedDate').gte(new Date('2015-08-21T20:37:45.176Z')).sort({ field: 'asc', test: -1 });",
    result = [],
    arr;

while(arr = re.exec(str)) {
  result.push(arr[1]);
  result.push(arr[2]);
}

document.getElementById('result').innerHTML = JSON.stringify(result, null, 2);

<pre id="result"></pre>

edited Aug 20, 2015 at 21:50

answered Aug 19, 2015 at 22:56

manji

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5 Comments

webteckie Over a year ago

Thanks. However, for some reason string.split in node is returning the following so the dots are being captured unlike in your demo: [ '', 'where', '(\'publishedDate\')', '.', 'gte', '(new Date(\'2015-08-21T20:37:45.176Z\'))', '.sort({ field: \'asc\', test: -1 })' ]

webteckie Over a year ago

Weird. If I do the same thing in the node console I get the same thing as you. But if I do it programatically via string split I get ..., ".sort({ field: 'asc', test: -1 })" where the .sort is not right.

manji Over a year ago

The input will be split by the matching tokens, so what you got is correct. If you want to extract those tokens only, see the code snippet I added.

webteckie Over a year ago

What would I do to the regex to make the semicolon in the input expression optional? If I change it to /(\w+)((.+?)(?=\.|;?))/g then I lose the parentheses around the 'new Date' expression.

manji Over a year ago

Change it to (?=\.|;|$), which means: dot or ; or $ (end of line). Regex updated in the answer to account for this case.

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