CODEWITHSUNDEEP
javascriptregex
Dan
Dan

Reputation: 2093

Javascript Regex - 9-digit number

I am trying to validate a variable contains a 9-digit number in Javascript. This should be basic but for some reason this is failing:

    var test = "123123123";
    var pattern = new RegExp("/\d{9}/");

    if(test.match(pattern))
    {
        //This code never executes
    }
    else
    {
        //This code is always executing
        alert('no match!'); 
    }

Can anyone see why I am not getting a match?

I also tried type-casting test to an integer with:

test = Number(test);

...but this doesn't work as it has to be a String to support the .match method.

Upvotes: 11

Views: 80253

Answers (5)

Michael Berkowski
Michael Berkowski

Reputation: 270607

When using a new Regexp() constructor, you should not include the / delimieters, since they are treated as literals in the expression.

Also your expression should be anchored ^$ to ensure it contains no other characters than the nine digits.

var test = "123123123";
// \d would need to be escaped as \\d in RegExp()
var pattern = new RegExp("^\\d{9}$");
// ..Or...
var pattern = new RegExp("^[0-9]{9}$");

Using a regular expression literal without new Regexp() is often a better strategy if you don't need to do string manipulations or include variables in the regex, since it avoids the extra backslash-escaping.

var pattern = /^\d{9}$/;

Upvotes: 5

Stefan Seemayer
Stefan Seemayer

Reputation: 2067

Try removing the slashes and escaping the backslash:

var test = "123123123";
var pattern = new RegExp("\\d{9}");

if(test.match(pattern))
{
    //This code never executes
    alert("match");
}
else
{
    //This code is always executing
    alert('no match!');
}

Upvotes: 1

Matt Ball
Matt Ball

Reputation: 359786

You're mixing the two different regex constructors. Pick one:

 var pattern = new RegExp("^\\d{9}$");
 // or
 var pattern = /^\d{9}$/;

N.B. you probably want to add start and end anchors (as above) to make sure the whole string matches.

Upvotes: 27

Jörg W Mittag
Jörg W Mittag

Reputation: 369448

You aren't looking for 9 consecutive digits, you are looking for 9 consecutive digits enclosed in slashes.

Upvotes: 2

vcsjones
vcsjones

Reputation: 141628

You are mixing regex literal syntax with the RegExp class. Try:

var test = "123123123";
var pattern = /\d{9}/;

if(test.match(pattern))
{
    alert('match!');
    //This code never executes
}
else
{
    //This code is always executing
    alert('no match!'); 
}​

Additionally, you may want to change your regex to match on the beginning and end of line if you want to ensure it contains only a 9 digit number. Right now the regex will match any string that contains a 9 digit number. You would change it like so:

var pattern = /^\d{9}$/;

Upvotes: 11

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