use named regex groups to output an array of matches

Question

I'm trying to get the hang of named capturing groups.

Given a string

var a = '{hello} good {sir}, a [great] sunny [day] to you.';

I'd like to output an array which maintains the integrity of the sentence (complete with punctuation, spaces, etc) so I can reassemble the sentence at a later time:

[
  {
    group: "braces",
    word: "hello"
  },
  {
    group: "other",
    word: " good " <-- space on either side is maintained
  },
  {
    group: "braces",
    word: "sir"
  },
  {
    group: "other",
    word: ", a "
  },
  {
    group: "brackets",
    word:  "great"
  },
  {
    group: "other",
    word: " sunny "
  },
  {
    group: "brackets",
    word: "day"
  },
  {
    group: "other",
    word:  " to you."
  },
]

I'm using named capturing groups to try and output this. <braces> captures any text within {}, <brackets> captures any text within [], and <others> captures anything else (\s,.\w+):

var regex = /(?<braces>\{(.*?)\})(?<brackets>\[(.*?)\])(?<others>\s,.\w+)?/g;

console.log(a.match(regex)); outputs nothing.

If I remove <others> group,

var regex = /(?<braces>\{(.*?)\})(?<brackets>\[(.*?)\])?/g;

console.log(a.match(regex)); outputs ["{hello}", "{sir}"]

Question: How do I use capturing groups to find all instances of named groups and output them like the above desired array?

CertainPerformance · Accepted Answer · 2020-11-11 23:44:31Z

3

A regex match object will only contain one string for a given named capture group. For what you're trying to do, you'll have to do it in two steps: first separate out the parts of the input, then map it to the array of objects while checking which group was captured to identify the sort of group it needs:

const str = '{hello} good {sir}, a [great] sunny [day] to you.';
const matches = [...str.matchAll(/{([^{]+)}|\[([^\]]+)\]|([^[{]+)/g)]
  .map(match => ({
    group: match[1] ? 'braces' : match[2] ? 'brackets' : 'other',
    word: match[1] || match[2] || match[3]
  }));
  
console.log(matches);

answered Nov 11, 2020 at 23:44

CertainPerformance

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