JavaScript Regex mismatch

Question

I have this code:

var regExp=new RegExp("(\/|-|.)+","g");

var t1=regExp.test(new Date());
alert(t1);//result true

var t2=regExp.test("19/03/1986");
alert(t1);//result true

why, first alert, return true value? There is not any charatter defined into regex pattern...

Thanks

. means any character. Also, you should learn about char class instead of using alternation groups — Thomas Ayoub
– Thomas Ayoub, Commented Oct 7, 2016 at 8:12
And besdies, the g modifier should be removed if you only use the regex with RegExp#test. The new Date() is passed to the regex as "2016-10-07T08:13:59.703Z" string that your regex matches entirely (since it is equal to .+), that is why the second test also succeeds. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Oct 7, 2016 at 8:13
The first test would match even with "(/|-)+" or "(/|-|\\.)+" as there is a - inside the input. But you'd better use var regExp= /[-\/.]/; here. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Oct 7, 2016 at 9:20

Byron · Accepted Answer · 2016-10-07 08:32:30Z

1

. means any char in regexp, so any char can match your exp

you can change it to \d{4}(\/|-|\.)\d{2}(\/|-|\.)\d{2}

Maybe this can help you understand what you write

Regexper

and remove g

edited Oct 7, 2016 at 8:32

answered Oct 7, 2016 at 8:23

Byron

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3 Comments

Daniel Cheung Over a year ago

"may help you understand" should be a comment, not an answer. An answer should be clear and straight forward, not just inspiring.

Byron Over a year ago

Apologize, I have changed the anwser

Wiktor Stribiżew Over a year ago

No, . does not match any char in JS regex. Do you understand why g should be removed?

C.Fasolin · Accepted Answer · 2016-10-07 09:31:30Z

0

I found a solution:

var regExp= /(\/|-|\.)/g;
var t1=regExp.test(new Date());
alert(t1);// return false
var t2=regExp.test("19/03/1986");
alert(t2);// return true

Thanks

answered Oct 7, 2016 at 9:31

C.Fasolin

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