How to use Nested RegEx

Question

I'm trying to convert this:
\/\*[^*\/]*(?:(?!\/\*|\*\/)[*\/][^*\/]*)*\*\/g
This is a nested Regex that works perfectly

/* one */
Stuff one
/* two /* three */ two */
Stuff two
/* four */

Into something like this:
a: {[^\}]*(?:(?!a: {|\})[\}][^\}]*)*\}g (Does not work properly)
I have been trying to get this to work for days now… no luck.

a: { one }
Stuff one
a: { two a: { three } two }
Stuff two
a: { four }

How it's suppose to work

source = "/* one */ Stuff one /* two  /* three */  two */ Stuff two /* four */"

regex = /\/\*[^*\/]*(?:(?!\/\*|\*\/)[*\/][^*\/]*)*\*\//g

results = source.match(regex)


$("body").append("<pre>" + JSON.stringify(results, null, 2) + "</pre>")

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

What I've done

source = "a: { one } Stuff one a: { two  a: { three }  two } Stuff two a: { four }"

regex = /a: {[^\}]*(?:(?!a: {|\})[\}][^\}]*)*\}/g

results = source.match(regex)


$("body").append("<pre>" + JSON.stringify(results, null, 2) + "</pre>")

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

What I've done… is showing this:
a: { one }
Stuff one
a: { two a: { three } two }
Stuff two
a: { four }

But it should be this
a: { one }
Stuff one
a: { two a: { three } two }
Stuff two
a: { four }

Some people, when confronted with a problem, think “I know, I'll use regular expressions.” Now they have two problems. - Jamie Zawinski — user177800
– user177800, Commented Oct 15, 2017 at 5:17
That will never work for the same reason nested tags in html will never work. Not a regular language. — user177800
– user177800, Commented Oct 15, 2017 at 5:18
You have something that works. Why are you changing it? What goal are you attempting to accomplish by changing it? You say "something like this" (showing something that's invalid syntax), but you don't say what it is about that which defines "like this". — Makyen
– Makyen ♦, Commented Oct 15, 2017 at 5:31
You don't "need a nested regexp". You have a problem, that you think the solution to might be a nested regexp. Actually, I don't even know what a "nested regexp" is. Is it a regexp with other regexps nested inside? Is it a regexp designed to match nested (recursive) grammars? is it a regexp designed to match only the innermost occurrences? — user663031
– user663031, Commented Oct 15, 2017 at 6:07

Monwell Partee · Accepted Answer · 2017-10-16 12:41:24Z

For capturing the deepest nest

use /\ba: {(?:(?!\ba: {.*}).)*?}/g

source = "a: { one } Stuff one a: { one a: { two a: { three } two} one } a: { one a: { two } one } fdsf dsae a: { one } Stuff two Stuff three a: { one a: { two a: { three a: { four } three} two} one } a: { one }"

regex = /\ba: {(?:(?!\ba: {.*}).)*?}/g
results = source.match(regex)


$("body").append("<pre>" + JSON.stringify(results, null, 2) + "</pre>")

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

For capturing entire nest

use /\ba: {.*?(?:(?!\ba: {.*}).)*}/g

source = "a: { one } Stuff one a: { one a: { two a: { three } two} one } a: { one a: { two } one } fdsf dsae a: { one } Stuff two Stuff three a: { one a: { two a: { three a: { four } three} two} one } a: { one }"

regex = /\ba: {.*?(?:(?!\ba: {.*}).)*}/g
results = source.match(regex)


$("body").append("<pre>" + JSON.stringify(results, null, 2) + "</pre>")

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

Has to be considered a nest

use /\ba: {[^}]*\ba: .*?(?:(?!\ba: {.*}).)*}/g

source = "a: { one } Stuff one a: { one a: { two a: { three } two} one } a: { one a: { two } one } fdsf dsae a: { one } Stuff two Stuff three a: { one a: { two a: { three a: { four } three} two} one } a: { one }"

regex = /\ba: {[^}]*\ba: .*?(?:(?!\ba: {.*}).)*}/g
results = source.match(regex)


$("body").append("<pre>" + JSON.stringify(results, null, 2) + "</pre>")

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

Organize both possible nest and true nests

use /\ba: {\s?[^}]*\ba: {.*?(?:(?!\ba: {.*}).)*}|(\ba: {.*?(?:(?!\ba: {.*}).)*})/g

source = "a: { one } Stuff one a: { one a: { two a: { three } two} one } a: { one a: { two } one } fdsf dsae a: { one } Stuff two Stuff three a: { one a: { two a: { three a: { four} three} two} one } a: { one }"

regex = /\ba: {\s?[^}]*\ba: {.*?(?:(?!\ba: {.*}).)*}|(\ba: {.*?(?:(?!\ba: {.*}).)*})/g
results = source.match(regex)

for (let i = 0; i < results.length; i++) {
  breakdown = regex.exec(source)

  if (breakdown[1]) {
    $(".box1").append(breakdown[1] + '<br>')
  } else {
    $(".box2").append(breakdown[0] + '<br>')
  }

}

.boxes {
  padding: 0px 30px;
  position: absolute;
}

.box2 {
  right: 0px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="boxes box1"></div>
<div class="boxes box2"></div>

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How to use Nested RegEx

How it's suppose to work

What I've done

1 Answer 1

For capturing the deepest nest

For capturing entire nest

Has to be considered a nest

Organize both possible nest and true nests

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Collectives™ on Stack Overflow

How it's suppose to work

What I've done

1 Answer 1

For capturing the deepest nest

For capturing entire nest

Has to be considered a nest

Organize both possible nest and true nests

Comments

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