Split string at first occurrence

Question

I'm struggling splitting the following string into two pieces. Mainly because the one of the possible delimiters is a space character, which can appear in the second capture group.

https://regex101.com/r/dS0bD8/1

How can I split these strings at either \s, \skeyword\s, or \skey\s?

'[] []' // => ['[]', '[]']
'[] keyword []' // => ['[]', '[]']
'[] key []' // => ['[]', '[]']

'[] ["can contain spaces"]'  // => ['[]', '["can contain spaces"]']
'[] keyword ["can contain spaces"]' // => ['[]', '["can contain spaces"]']
'[] key ["can contain spaces"]' // => ['[]', '["can contain spaces"]']

'{} {}' // => ['{}', '{}']
'{} keyword {}' // => ['{}', '{}']
'{} key {}' // => ['{}', '{}']

'{} {"can":"contain spaces"}' // => ['{}', '{"can":"contain spaces"}']
'{} keyword {"can":"contain spaces"}' // => ['{}', '{"can":"contain spaces"}']
'{} key {"can":"contain spaces"}' // => ['{}', '{"can":"contain spaces"}']

'string string' // => ["string", "string"]
'string keyword string' // => ["string", "string"]
'string key string' // => ["string", "string"]

You want to use a single regex to match all the previous cases ? — ismnoiet
– ismnoiet, Commented Apr 25, 2016 at 23:38
What about taking a step back and removing all instances of keyword and key then using Regex? — Sumner Evans
– Sumner Evans, Commented Apr 25, 2016 at 23:40
What's wrong with the regex you have? Note that this tool is using a test STRING singular, and is therefore assuming that everything in the input is one long string, when you are intending for them to be multiple individual strings. — Hamms
– Hamms, Commented Apr 25, 2016 at 23:40
@SumnerEvans I'm curious how you can have or options and only match the first instance. It's apart of the question. — ThomasReggi
– ThomasReggi, Commented Apr 25, 2016 at 23:41

James Buck · Accepted Answer · 2016-04-25 23:58:29Z

8

(\skeyword\s|\skey\s|\s(?=.*[\[{]|[^\]}]+$))

Will work for all the cases you gave.
Demo here.

edited Apr 25, 2016 at 23:58

answered Apr 25, 2016 at 23:47

James Buck

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4 Comments

ThomasReggi Over a year ago

This is amazing. Thank you James! Unfortunately the string string case needs to include alpha-numeric and symbols not just word characters. How can I add this in? :) (\skeyword\s|\skey\s|\s(?=.*[\[{]|[a-z0-9-]+$))?

ThomasReggi Over a year ago

@JamesBuck hey, just found this fails {} {"can": []} you have any idea how to fix this?

ThomasReggi Over a year ago

@JamesBuck is there any way to only capture the first space? It's an odd bug.

James Buck Over a year ago

@ThomasReggi you could try a negative lookahead instead to verify the space is not inside a {} or [] block - (\skeyword\s|\skey\s|\s(?![^[]+]$|[^{]+}$)). Regex demo. I don't know a way to check it's the first space without using a lookbehind or \K reset (both of which the JavaScript regex engine doesn't support).

guest271314 · Accepted Answer · 2016-04-26 00:00:43Z

3

You can replace "keyword" and "key" with empty string "", then split \s+

str.replace(/keyword|key/g, "").split(/\s+/)

answered Apr 26, 2016 at 0:00

guest271314

1

1 Comment

guest271314 Over a year ago

@ThomasReggi You could alternatively replace keyword|key with comma character , then call .split(/,/)

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