I'm trying to write a regex for country code, which should limit to four characters maximum, only symbol allowed is a + sign. When the + is used, the + has to be in the beginning, and it should have at least one number.
Valid cases
+1
1
+12
12
+123
1234
Invalid cases
+
+1234
12345
1+
12+
<empty>
etc.
The expression that I have right now.
/(\+\d{1,3})/
Can it be more elegant?
-Thank you in advance!!
This should work. I used
/^(\+?\d{1,3}|\d{1,4})$/
See results
Edit:
The //gm flags are global and multiline, respectively. You need those if you have a string that can have multiple places to match a country code, or there are multiple lines in your string. If your string is going to be more than just a possible country code, you'd need to get rid of the ^ and $ at the beginning and end of the regex. To use the regex, you'd want something like this:
var regex = /^(\+?\d{1,3}|\d{1,4})$/gm
var str = "+123"
var match = str.match(regex);
//match is an array, with one result in this case. So match[0] == "+123"
You need to make a case differentiation. Either with or without leading plus sign:
(\+\d{1-3})|(\d{1,4})
Whether you want to anchor the expression to line limits (^ and $) or check for leading or trailing white spaces or the like obviously depends on your situation.
country codes can be of following types
+1
+91
+223
+1-224
The javascript regex that makes sure that the input is one if the
/^\+(\d{1}\-)?(\d{1,3})$/
I prepared this according to wikipedia article, for parsing correct information for 1 or 2 digit country codes this is much more efficient, but needs improvement for subterritories if you need them;
(?:\+|00)(1|7|2[07]|3[0123469]|4[013456789]|5[12345678]|6[0123456]|8[1246]|9[0123458]|(?:2[12345689]|3[578]|42|5[09]|6[789]|8[035789]|9[679])\d)
Related
I have a scenario where I need to find and replace a number in a large string using javascript. Let's say I have the number 2 and I want to replace it with 3 - it sounds pretty straight forward until I get occurrences like 22, 32, etc.
The string may look like this:
"note[2] 2 2_ someothertext_2 note[32] 2finally_2222 but how about mymomsays2."
I want turn turn it into this:
"note[3] 3 3_ someothertext_3 note[32] 3finally_2222 but how about mymomsays3."
Obviously this means .replace('2','3') is out of the picture so I went to regex. I find it easy to get an exact match when I am dealing with string start to end ie: /^2$/g. But that is not what I have. I tried grouping, digit only, wildcards, etc and I can't get this to match correctly.
Any help on how to exactly match a number (where 0 <= number <= 500 is possible, but no constraints needed in regex for range) would be greatly appreciated.
The task is to find (and replace) "single" digit 2, not embedded in
a number composed of multiple digits.
In regex terms, this can be expressed as:
Match digit 2.
Previous char (if any) can not be a digit.
Next char (if any) can not be a digit.
The regex for the first condition is straightforward - just 2.
In other flavours of regex, e.g. PCRE, to forbid the previous
char you could use negative lookbehind, but unfortunately Javascript
regex does not support it.
So, to circumvent this, we must:
Put a capturing group matching either start of text or something
other than a digit: (^|\D).
Then put regex matching just 2: 2.
The last condition, fortunately, can be expressed as negative lookahead,
because even Javascript regex support it: (?!\d).
So the whole regex is:
(^|\D)2(?!\d)
Having found such a match, you have to replace it with the content
of the first capturing group and 3 (the replacement digit).
You can use negative look-ahead:
(\D|^)2(?!\d)
Replace with: ${1}3
If look behind is supported:
(?<!\d)2(?!\d)
Replace with: 3
See regex in use here
(\D|\b)2(?!\d)
(\D|\b) Capture either a non-digit character or a position that matches a word boundary
(?!\d) Negative lookahead ensuring what follows is not a digit
Alternations:
(^|\D)2(?!\d) # Thanks to #Wiktor in the comments below
(?<!\d)2(?!\d) # At the time of writing works in Chrome 62+
const regex = /(\D|\b)2(?!\d)/g
const str = `note[2] 2 2_ someothertext_2 note[32] 2finally_2222 but how about mymomsays2.`
const subst = "$13"
console.log(str.replace(regex, subst))
I'm relative new to RegEx and I've encountered a problem. I want to regex a name. I want it to be max 100 characters, contain at least 2 alphabetic characters and it will allow the character '-'.
I have no problem to only check for alphabetic characters or both alphabetic characters and hyphen but I dont't want a name that potantially can be '---------'.
My code without check for hyphens is
var nameRegExp = /^([a-z]){2,100}$/;
An explanation for the code is appreciated as well.
Thanks!
I guess
/^(?=.*[a-z].*[a-z])[a-z-]{1,100}$/
the lookahead part (^(?=.*[a-z].*[a-z])) checks if there are at least two letters. This pattern ("start of string, followed by...") is a common way to express additional conditions in regexes.
You can limit the number of - by adding a negative assertion, as #Mike pointed out:
/^(?=.*[a-z].*[a-z])(?!(?:.*-){11,})[a-z-]{1,100}$/ // max 10 dashes
however it might be easier to write an expression that would match "good" strings instead of trying to forbid "bad" ones. For example, this
/^[a-z]+(-[a-z]+)*$/
looks like a good approximation for a "name". It allows foo and foo-bar-baz, but not the stuff like ---- or foo----bar----.
To limit the number of - you could add a negative look-ahead, where the number 3 is one more than the maximum number you want to allow
/^(?!(?:[a-z]*-){3,})(?=-*[a-z]-*[a-z])[a-z-]{2,100}$/
Not a big user of RegEx - never really understood them! However, I feel the best way to check input for a username field would be with one that only allows Letters (upper or lower), numbers and the _ character, and must start with a letter as per the site policy. The My RegEx and code is as such:
var theCheck = /[a-zA-Z]|\d|_$/g;
alert(theCheck.test(theUsername));
Despite trying with various combinations, everything is returning "true".
Can anyone help?
Your regex is saying "does theUsername contain a letter, digit, or end with underscore".
Try this instead:
var theCheck = /^[a-z]([a-z_\d]*)$/i; // the "i" is "ignore case"
This says "theUsername starts with a letter and only contains letters, digits, or underscores".
Note: I don't think you need the "g" here, that means "all matches". We just want to test the whole string.
How about something like this:
^([a-zA-Z][a-zA-Z0-9_]{3,})$
To explain the entire pattern:
^ = Makes sure that the first pattern in brackets is at the beginning
() = puts the entire pattern in a group in case you need to pull it out and not just validate
a-zA-Z0-9_ = matches your character allowances
$ = Makes sure that this must be the entire line
{3,} = Makes sure there are a minimum of 3 characters.
You can add a number after the comma for a character limit max
You could also use a +, which would merely enforce at least one character match the second pattern. A * would not enforce any lengths
Use this as your regex:
^[A-Za-z][a-zA-Z0-9_]*$
I have to get the number of parenthesized substring matches in a regular expression:
var reg=/([A-Z]+?)(?:[a-z]*)(?:\([1-3]|[7-9]\))*([1-9]+)/g,
nbr=0;
//Some code
alert(nbr); //2
In the above example, the total is 2: only the first and the last couple of parentheses will create grouping matches.
How to know this number for any regular expressions?
My first idea was to check the value of RegExp.$1 to RegExp.$9, but even if there are no corresponding parenthseses, these values are not null, but empty string...
I've also seen the RegExp.lastMatch property, but this one represents only the value of the last matched characters, not the corresponding number.
So, I've tried to build another regular expression to scan any RegExp and count this number, but it's quite difficult...
Do you have a better solution to do that?
Thanks in advance!
Javascripts RegExp.match() method returns an Array of matches. You might just want to check the length of that result array.
var mystr = "Hello 42 world. This 11 is a string 105 with some 2 numbers 55";
var res = mystr.match(/\d+/g);
console.log( res.length );
Well, judging from the code snippet we can assume that the input pattern is always a valid regular expression, because otherwise it would fail before the some code partm right? That makes the task much easier!
Because We just need to count how many starting capturing parentheses there are!
var reg = /([A-Z]+?)(?:[a-z]*)(?:\([1-3]|[7-9]\))*([1-9]+)/g;
var nbr = (' '+reg.source).match(/[^\\](\\\\)*(?=\([^?])/g);
nbr = nbr ? nbr.length : 0;
alert(nbr); // 2
And here is a breakdown:
[^\\] Make sure we don't start the match with an escaping slash.
(\\\\)* And we can have any number of escaped slash before the starting parenthes.
(?= Look ahead. More on this later.
\( The starting parenthes we are looking for.
[^?] Make sure it is not followed by a question mark - which means it is capturing.
) End of look ahead
Why match with look ahead? To check that the parenthes is not an escaped entity, we need to capture what goes before it. No big deal here. We know JS doens't have look behind.
Problem is, if there are two starting parentheses sticking together, then once we capture the first parenthes the second parenthes would have nothing to back it up - its back has already been captured!
So to make sure a parenthes can be the starting base of the next one, we need to exclude it from the match.
And the space added to the source? It is there to be the back of the first character, in case it is a starting parenthes.
How do I remove numbers from a string using Javascript?
I am not very good with regex at all but I think I can use with replace to achieve the above?
It would actually be great if there was something JQuery offered already to do this?
//Something Like this??
var string = 'All23';
string.replace('REGEX', '');
I appreciate any help on this.
\d matches any number, so you want to replace them with an empty string:
string.replace(/\d+/g, '')
I've used the + modifier here so that it will match all adjacent numbers in one go, and hence require less replacing. The g at the end is a flag which means "global" and it means that it will replace ALL matches it finds, not just the first one.
Just paste this into your address bar to try it out:
javascript:alert('abc123def456ghi'.replace(/\d+/g,''))
\d indicates a character in the range 0-9, and the + indicates one or more; so \d+ matches one or more digits. The g is necessary to indicate global matching, as opposed to quitting after the first match (the default behavior).