Debugging regular expressions in JavaScript

Question

In Python, there is a special re.DEBUG flag that would display the regular expression parse tree:

>>> import re
>>>
>>> data = "myid_01234"
>>> re.match(r"^myid_(\d+)$", data, re.DEBUG)
at at_beginning
literal 109
literal 121
literal 105
literal 100
literal 95
subpattern 1
  max_repeat 1 4294967295
    in
      category category_digit
at at_end
<_sre.SRE_Match object at 0x104ffe7b0>

Is it possible to get a similar debug information with a parse tree in JavaScript?

> var re = /^myid_(\d+)$/;
> var data = "myid_01234"
> data.match(re)
["myid_01234", "01234"]

Peter Mortensen · Accepted Answer · 2018-07-26 19:24:55Z

4

+100

JavaScript does not offer this.

But you can use an online service or software to debug it. Example: https://regex101.com/r/vY0iK9/1

edited Jul 26, 2018 at 19:24

Peter Mortensen

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answered Sep 22, 2015 at 14:41

Cyrbil

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2 Comments

Mariano Over a year ago

debuggex.com is also a nice tool to manually advance a match attempt

Cyrbil Over a year ago

I used debuggex for a long time, the graphing feature is pretty neat. These site have both pretty much the same functionality, so I guess it's a matter of opinion.

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