I have a text field which accepts only one character but if user enters any escape characters such as \n, \t, \s, etc it should be allowing it even though it has 2 characters.
I am using jquery.validationEngine to validate the text field but failing to parse it as per my desire.
A regular expression for that could be
[^\\]|\\[tns]
Meaning
any char except a backslash
or a backslash followed by t, n or s
Note that if you need to put this in a string literal then backslashes must be doubled again (doubled once for the string and doubled again to escape their special meaning in a regexp).
Related
I tried to write a form validation for description textarea> of the users about their owns like he/she education or experience.
I wrote this Regex for this textarea, but I have a problem if user use above comma it's not allowed, for example if user written "House's", it's not allowing to write this comma '.
PWhich symbols may needed or predicate while users describe owns?
I used this Regex:
$descriptionValidation = "/^[a-zA-Z0-9\.\-\,\"\(\) ]+[a-zA-Z0-9\.\-\,\"\(\) ]*$/";
To match a whole string and require that the string only consist of alphanumeric characters and: dots, commas, single-quotes (also called apostrophes, but not "above commas"), double-quotes, left parentheses, right parentheses, spaces, and hyphens, use the following expression.
The ^ and $ metacharacters ensure that the characters span the entire length of the string. + means one or more of the any of the characters in the list. The "list" is technically called a "character class". a-z is the full range of letters and \d is the full range of numbers. - does have special meaning inside of a character class but only if it has a non-ranged expression on both sides of it. If you wish to prevent mistakes with hyphens inside of a character class, you can add a backslash to escape it or you can write the hyphen at the start or end of the character class OR you can write it next to a character range.
/^[a-z\d.,'"() -]+$/i
When declaring this pattern in php using single quotes, you will need to escape the single-quote in the character class.
$descriptionValidation = '/^[a-z\d.,\'"() -]+$/i';
I'm trying to understand the backslash and how to use escaping like: \ in regular expressions.
I've read that when using strings its named to escape a string.
But what does that actually mean?
Many characters in regular expressions have special meanings. For instance, the dot character '.' means "any one character". There are a great deal of these specially-defined characters, and sometimes, you want to search for one, not use its special meaning.
See this example to search for any filename that contains a '.':
/^[^.]+\..+/
In the example, there are 3 dots, but our description says that we're only looking for one. Let's break it down by the dots:
Dot #1 is used inside a "character class" (the characters inside the square brackets), which tells the regex engine to search for "any one character" that is not a '.', and the "+" says to keep going until there are no more characters or the next character is the '.' that we're looking for.
Dot #2 is preceded by a backslash, which says that we're looking for a literal '.' in the string (without the backslash, it would be using its special meaning, which is looking for "any one character"). This dot is said to be "escaped", because it's special meaning is not being used in this context - the backslash immediately before it made that happen.
Dot #3 is simply looking for "any one character" again, and the '+' following it says to keep doing that until it runs out of characters.
So, the backslash is used to "escape" the character immediately following it; as such, it's called the "escape character". That just means that the character's special meaning is taken away in that one place.
Now, escaping a string (in regex terms) means finding all of the characters with special meaning and putting a backslash in front of them, including in front of other backslash characters. When you've done this one time on the string, you have officially "escaped the string".
Say you try to print out a string, let's say "this\that".
That \ character is recognized as a special character. I'm not sure about regex, but say in Java or C, \t will tab the rest of the string over, so it would print as
this hat
But the \ "escapes" a character from the string, deriving it of regular meaning, so using "this\that" instead would result in
this\that
I hope this helped.
Quoting from MSDN:
The backslash (\) in a regular expression indicates one of the following:
The character that follows it is a special character, as shown in the table in the following section. For example, \b is an anchor that indicates that a regular expression match should begin on a word boundary, \t represents a tab, and \x020 represents a space.
A character that otherwise would be interpreted as an unescaped language construct should be interpreted literally. For example, a brace ({) begins the definition of a quantifier, but a backslash followed by a brace (\{) indicates that the regular expression engine should match the brace. Similarly, a single backslash marks the beginning of an escaped language construct, but two backslashes (\) indicate that the regular expression engine should match the backslash.
I have a regular expression in JavaScript to allow numeric and (,.+() -) character in phone field
my regex is [0-9-,.+() ]
It works for numeric as well as above six characters but it also allows characters like % and $ which are not in above list.
Even though you don't have to, I always make it a point to escape metacharacters (easier to read and less pain):
[0-9\-,\.+\(\) ]
But this won't work like you expect it to because it will only match one valid character while allowing other invalid ones in the string. I imagine you want to match the entire string with at least one valid character:
^[0-9\-,\.\+\(\) ]+$
Your original regex is not actually matching %. What it is doing is matching valid characters, but the problem is that it only matches one of them. So if you had the string 435%, it matches the 4, and so the regex reports that it has a match.
If you try to match it against just one invalid character, it won't match. So your original regex doesn't match the string %:
> /[0-9\-,\.\+\(\) ]/.test("%")
false
> /[0-9\-,\.\+\(\) ]/.test("44%5")
true
> "444%6".match(/[0-9\-,\.+\(\) ]/)
["4"] //notice that the 4 was matched.
Going back to the point about escaping, I find that it is easier to escape it rather than worrying about the different rules where specific metacharacters are valid in a character class. For example, - is only valid in the following cases:
When used in an actual character class with proper-order such as [a-z] (but not [z-a])
When used as the first or last character, or by itself, so [-a], [a-], or [-].
When used after a range like [0-9-,] or [a-d-j] (but keep in mind that [9-,] is invalid and [a-d-j] does not match the letters e through f).
For these reasons, I escape metacharacters to make it clear that I want to match the actual character itself and to remove ambiguities.
You just need to anchor your regex:
^[0-9-,.+() ]+$
In character class special char doesn't need to be escaped, except ] and -.
But, these char are not escaped when:
] is alone in the char class []]
- is at the begining [-abc] or at the end [abc-] of the char class or after the last end range [a-c-x]
Escape characters with special meaning in your RegExp. If you're not sure and it isn't an alphabet character, it usually doesn't hurt to escape it, too.
If the whole string must match, include the start ^ and end $ of the string in your RegExp, too.
/^[\d\-,\.\+\(\) ]*$/
I want to have a regex for text field in ExtJs(maskRe) which matches all java code pattern
I've used
maskRe:/^[A-Za-z0-9 _=//~'"|{}();*:?+,.]*$/
I also want to include [,], but it seems /[, /], //[, //] is not working..
Any inputs please
The problem is you need to escape your forward slash. Change // to \/:
/^[A-Za-z0-9 _=\/~'"|{}();*:?+,.]*$/
However this regular expression does not match any Java code. Java code can contain almost any Unicode character. int møøse = 42; is valid Java.
To strip special characters from its magic powers you have to escape them, by putting backslash \ in front of character. I.e. to match [ you type \[.
And since backslash acts as special character as well, to match it literally, you escape it the same way: \\.
And since you used / as patter delimiter, you need to escape its occurrences within pattern:
/^[A-Za-z0-9 _=\/~'"|{}();*:?+,.]*$/
The way to escape regex meta-characters is using a backslash (\), not a forwards slash (/).
[,] should be \[,\]
// should be \/
I need to match these characters. This quote is from an API documentation (external to our company):
Valid characters: 0-9 A-Z a-z & # - . , ( ) / : ; ' # "
I used this Regex to match characters:
^[0-9a-z&#-\.,()/:;'""#]*$
However, this wrongly matches characters like %, $, and many other characters. What's wrong?
You can test this regular expression online using http://regexhero.net/tester/, and this regular expression is meant to work in both .NET and JavaScript.
You are not escaping the dash -, which is a reserved character. If you add replace the dash with \- then the regex no longer matches those characters between # and \
Move the literal - to the front of the character set:
^[-0-9a-z&#\.,()/:;'""#]*$
otherwise it is taken as specifying a range like when you use it in 0-9.
- sign, when not escaped, has special meaning in square brackets. #-\. is transformed into #-. (BTW, backslash before dot is not necessary in square brackets), which means "any character between # (ASCII 0x23) and . (ASCII 0x2E). The correct notation is
^[0-9a-z&#\-.,()/:;'"#]*$
The special characters in a character class are the closing bracket (]), the backslash (\), the caret (^) and the hyphen (-).
As such, you should either escape them with a backslash (\), or put them in a position where there is no ambiguity and they do not need escaping. In the case of a hyphen, this would be the first or last position.
You also do not need to escape the dot (.).
Your regex thus becomes:
^[-0-9a-z&#.,()/:;'"#]*$
As a side note, there are many available regex evaluators which provide code hinting. This way, you can simply hover your mouse over your regular expression and it can be explained in English words.
One such free one is RegExr.
Typing your original regex in it and hovering over the hyphen shows:
Matches characters in the range '#-\'
Try that
^[0-9a-zA-Z\&\#\-\.\,\(\)\/\:\;\'\"\#]*$