javascript regex to require at least one special character

Question

I've seen plenty of regex examples that will not allow any special characters. I need one that requires at least one special character.

I'm looking at a C# regex

var regexItem = new Regex("^[a-zA-Z0-9 ]*$");

Can this be converted to use with javascript? Do I need to escape any of the characters?

Based an example I have built this so far:

var regex = "^[a-zA-Z0-9 ]*$";

//Must have one special character
if (regex.exec(resetPassword)) {
    isValid = false;
    $('#vsResetPassword').append('Password must contain at least 1 special character.');
}

Can someone please identify my error, or guide me down a more efficient path? The error I'm currently getting is that regex has no 'exec' method

Have you looked at any documentation on how Javascript uses regexes? — Waleed Khan, Feb 15 '13 at 21:30
Consider http://stackoverflow.com/questions/3802192/regexp-java-for-password-validation — Tomalak, Feb 15 '13 at 21:36
@AlexWayne, I don't set requirements, I'm just a coding monkey ;) — Jon Harding, Feb 15 '13 at 21:49

score 3 · Answer 1 · answered Feb 15 '13 at 21:32

3

In javascript, regexs are formatted like this:

/^[a-zA-Z0-9 ]*$/

Note that there are no quotation marks and instead you use forward slashes at the beginning and end.

answered Feb 15 '13 at 21:32

lmortenson

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score 3 · Accepted Answer · answered Feb 15 '13 at 21:33

3

Your problem is that "^[a-zA-Z0-9 ]*$" is a string, and you need a regex:

var regex = /^[a-zA-Z0-9 ]*$/;                 // one way
var regex = new RegExp("^[a-zA-Z0-9 ]*$");     // another way

[more information]

Other than that, your code looks fine.

answered Feb 15 '13 at 21:33

ruakh

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You fixed his error but this is disallowing anything except a-z, A-Z, 0-9, or spaces. It's not requiring a special character. – Dominic May 04 '16 at 21:42
@DominicTobias: This regex will *match* a string that contains no special characters, but it, in and of itself, doesn't "require" or "disallow" anything. Rather, the OP's code will reject any password that matches this regex; so it requires the password to contain at least one special character, by disallowing any password that doesn't. – ruakh May 04 '16 at 22:41
Ah yeah, perhaps that's a better approach than looking for a specific list of characters – Dominic May 05 '16 at 08:36
@DominicTobias: I think either approach is equally fine. (You don't need a *specific* list of special characters; the complement of this regex is just `/[^a-zA-Z0-9 ]/`.) Regexes are an incredibly powerful tool, but so is `!`. :-) – ruakh May 05 '16 at 19:36

score 1 · Answer 3 · answered Feb 15 '13 at 21:35

In javascript, you can create a regular expression object two ways.

1) You can use the constructor method with the RegExp object (note the different spelling than what you were using):

var regexItem = new RegExp("^[a-zA-Z0-9 ]*$");

2) You can use the literal syntax built into the language:

var regexItem = /^[a-zA-Z0-9 ]*$/;

The advantage of the second is that you only have to escape a forward slash, you don't have to worry about quotes. The advantage of the first is that you can programmatically construct a string from various parts and then pass it to the RegExp constructor.

Further, the optional flags for the regular expression are passed like this in the two forms:

var regexItem = new RegExp("^[A-Z0-9 ]*$", "i");
var regexItem = /^[A-Z0-9 ]*$/i;

In javascript, it seems to be a more common convention to the user /regex/ method that is built into the parser unless you are dynamically constructing a string or the flags.

javascript regex to require at least one special character

3 Answers3