Why doesn't String#match() result contain captured values?

Question

I am trying to extract a value from simplest JSON in javascript.

After searching i found match to be closest solution.

But trying this with grouping of RegExp, it does not give suitable result.

My object is {"a":"one"} and regex i am building is new RegExp('{"a":"(.*)"}','g')

my results with

'{"a":"one"}'.match(new RegExp('{"a":"(.*)"}','g')) is ["{"a":"one"}"]

'{"a":"one"}'.match(new RegExp('{"a":"(.*)"}'.replace(/([+?^=!:${}|\[\]\/\\])/g, "\\$1"),'g'))

is also ["{"a":"one"}"]

I am expecting the result should have been ["{"a":"one"}", "one"]

what wrong is happening here?

You are using a global modifier with `String#match`, so all captures are omitted. — Wiktor Stribiżew, Sep 16 '16 at 11:07
@codeofnode Tushar already posted it - use the builtin JSON parser. — Bergi, Sep 16 '16 at 11:27
@Bergi i do not know what my key going to be and i even don't know at which level i would find.. — codeofnode, Sep 16 '16 at 11:29
@codeofnode If the name of the property is dynamic, [use bracket notation](http://stackoverflow.com/q/4244896/1048572), if the object is arbitrarily nested [use recursion](http://stackoverflow.com/q/11922383/1048572). If you don't know how, please [ask a new question](http://stackoverflow.com/questions/ask) with your actual problem. Regex is not a solution. — Bergi, Sep 16 '16 at 11:32

Wiktor Stribiżew · Accepted Answer · 2020-04-22T16:33:29.377

See String#match() reference:

If the regular expression includes the g flag, the method returns an Array containing all matched substrings rather than match objects. Captured groups are not returned.

Remove g modifier to get the expected results.

console.log(
   '{"a":"one"}'.match(/{"a":"(.*)"}/)
);

Or, if you need to get multiple matches, use `RegExp#exec` in a loop or - with the latest JS environments - `String#matchAll`:

<!-- begin snippet: js hide: false console: true babel: false -->

And the matchAll variant:

const s = '{"a":"one","a":"two"}', regex = /"a":"([^"]*)"/g;
const results = Array.from([...s.matchAll(regex)], m => m[1]);
console.log(results);

Why doesn't String#match() result contain captured values?

1 Answers1

Linked

Related