CODEWITHSUNDEEP
javascriptregex
Xandrmoro
Xandrmoro

Reputation: 93

Javascript regex always returns true

var re = /^\[*:*\]*/;
alert(re.test("aa"));

Always alerts true (on any string). What am i doing wrong? I need to check is there something like [445:123] in the beginning of the string.

Upvotes: 1

Views: 480

Answers (3)

Pointy
Pointy

Reputation: 414016

Your regex means

  • at the start of the string ...
  • there can be zero or more [ characters ...
  • then zero or more : characters ...
  • then zero or more ] characters.

The string "aa" matches that. You probably want something like:

var re = /^\[\d+:\d+\]/;

The + quantifier means "one or more", while * means "zero or more". The \d escape means "any digit".

*edit — if the regex needs to match something like

[12:2:17:419]

as well, then it would be

var re = /^\[\d+(:\d+)+\]/;

Upvotes: 5

Billy Moon
Billy Moon

Reputation: 58619

in regular expressions, * does not mean wildcard match, it means zero or more of the previous token. To match any character, use . instead. A regex for what you want to match is more like this...

/^\[.*:.*\].*/

But better is to be more specific, using \d to match decimals, and use + to match one or more of the previous token, and remove the erroneous characters after the match...

/^\[\d+:\d+\]/

Upvotes: 0

Josh
Josh

Reputation: 1553

You're checking for any number of [, followed by any number of :, followed by any number of ]. Note that that's any number - 0 occurrences of any of those is a valid result.

What it sounds like you mean to do is something more like var re= /^\[\d+:\d+\]/;

Upvotes: 1

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