I want to ensure that the user input doesn't contain characters like <, > or &#, whether it is text input or textarea. My pattern:
var pattern = /^((?!&#|<|>).)*$/m;
The problem is, that it still matches multiline strings from a textarea like
this text matches
though this should not, because of this character <
EDIT:
To be more clear, I need exclude &# combination only, not & or #.
Please suggest the solution. Very grateful.
You're probably not looking for m (multiline) switch but s (DOTALL) switch in Javascript. Unfortunately s doesn't exist in Javascript.
However good news that DOTALL can be simulated using [\s\S]. Try following regex:
/^(?![\s\S]*?(&#|<|>))[\s\S]*$/
OR:
/^((?!&#|<|>)[\s\S])*$/
Live Demo
I don't think you need a lookaround assertion in this case. Simply use a negated character class:
var pattern = /^[^<>&#]*$/m;
If you're also disallowing the following characters, -, [, ], make sure to escape them or put them in proper order:
var pattern = /^[^][<>&#-]*$/m;
Alternate answer to specific question:
anubhava's solution works accurately, but is slow because it must perform a negative lookahead at each and every character position in the string. A simpler approach is to use reverse logic. i.e. Instead of verifying that: /^((?!&#|<|>)[\s\S])*$/ does match, verify that /[<>]|&#/ does NOT match. To illustrate this, lets create a function: hasSpecial() which tests if a string has one of the special chars. Here are two versions, the first uses anubhava's second regex:
function hasSpecial_1(text) {
// If regex matches, then string does NOT contain special chars.
return /^((?!&#|<|>)[\s\S])*$/.test(text) ? false : true;
}
function hasSpecial_2(text) {
// If regex matches, then string contains (at least) one special char.
return /[<>]|&#/.test(text) ? true : false;
}
These two functions are functionally equivalent, but the second one is probably quite a bit faster.
Note that when I originally read this question, I misinterpreted it to really want to exclude HTML special chars (including HTML entities). If that were the case, then the following solution will do just that.
Test if a string contains HTML special Chars:
It appears that the OP want to ensure a string does not contain any special HTML characters including: <, >, as well as decimal and hex HTML entities such as: , , etc. If this is the case then the solution should probably also exclude the other (named) type of HTML entities such as: &, <, etc. The solution below excludes all three forms of HTML entities as well as the <> tag delimiters.
Here are two approaches: (Note that both approaches do allow the sequence: &# if it is not part of a valid HTML entity.)
FALSE test using positive regex:
function hasHtmlSpecial_1(text) {
/* Commented regex:
# Match string having no special HTML chars.
^ # Anchor to start of string.
[^<>&]* # Zero or more non-[<>&] (normal*).
(?: # Unroll the loop. ((special normal*)*)
& # Allow a & but only if
(?! # not an HTML entity (3 valid types).
(?: # One from 3 types of HTML entities.
[a-z\d]+ # either a named entity,
| \#\d+ # or a decimal entity,
| \#x[a-f\d]+ # or a hex entity.
) # End group of HTML entity types.
; # All entities end with ";".
) # End negative lookahead.
[^<>&]* # More (normal*).
)* # End unroll the loop.
$ # Anchor to end of string.
*/
var re = /^[^<>&]*(?:&(?!(?:[a-z\d]+|#\d+|#x[a-f\d]+);)[^<>&]*)*$/i;
// If regex matches, then string does NOT contain HTML special chars.
return re.test(text) ? false : true;
}
Note that the above regex utilizes Jeffrey Friedl's "Unrolling-the-Loop" efficiency technique and will run very quickly for both matching and non-matching cases. (See his regex masterpiece: Mastering Regular Expressions (3rd Edition))
TRUE test using negative regex:
function hasHtmlSpecial_2(text) {
/* Commented regex:
# Match string having one special HTML char.
[<>] # Either a tag delimiter
| & # or a & if start of
(?: # one of 3 types of HTML entities.
[a-z\d]+ # either a named entity,
| \#\d+ # or a decimal entity,
| \#x[a-f\d]+ # or a hex entity.
) # End group of HTML entity types.
; # All entities end with ";".
*/
var re = /[<>]|&(?:[a-z\d]+|#\d+|#x[a-f\d]+);/i;
// If regex matches, then string contains (at least) one special HTML char.
return re.test(text) ? true : false;
}
Note also that I have included a commented version of each of these (non-trivial) regexes in the form of a JavaScript comment.
Related
I have thought of an example that I can use to learn it well. I designed a kind of "script language" (as a string) that I want to parse and interpret.
PS: Yes, it reminds of LINQ a bit, but that's just a coincidence.
The first thing I thought about, I want to remove all the comments, because these shouldn't be interpreted.
I only look for comments like: /*...*/ and //...\n
However, these should of course not happen within quotation marks: "..." and '...'
But how can I use RegEx to find comments that are not inside quotation marks?
String:
//get means only read, but not to mutate data
Get(BooksWithAuthors)
//default queries via mycel
.Query()
//junction table to pair books and authors
.From(BookAuthor.As(BA))
//main table for books
.Join(left: Books.As(B) => B.Id == BA.BookId)
//main table for authors
.Join(left: Authors.As(A) => A.Id == BA.AuthorId)
//groups by column, body allows to restore data (restructuring)
.GroupBy(B.Id, => B.Authors.Add(A))
//ignore still registerd data objects for the response
.SelectIgnore(BA)
//or select only that fields or objects you want to response
.Select(B)
.Foo("//wrong-comment-inside-quotes")
.Foo('//wrong-comment-inside-single-quotes')
.Foo('some /*wrong-comment*/ inside')
;
//get means only read, but not to mutate data
Get(BooksWithAuthorsByMethod)
//using individual backside methods (created by own)
.GetBooksWithAuthors(id:6, filter:{key:'minAuthorAge', value:17})
;
/*
comments
"over"
'multiply
lines' //with wrong comments inside
*\
RegEx:
.*[^'"].*([\/]{2}.*[\r\n|\r|\n]).*[^'"].*
(https://regex101.com/r/zPzBFj/1)
Yeah, I tried it only with //, but not every incidence was found and it also matches that comments within quotation marks. Maybe ?! is not the right way. But how can I do that?
I'm sure I'll have one or two more questions about this example. But as I said, I'm still learning RegEx, so step by step...
If you match the string with the regular expression
/'.*?'|".*?"|(\/\/[^\r\n]*|\/\*.*?\*\/)/gs
comments will be saved to capture group 1. The idea is to match but not capture what you don't want and match and capture what you do want. Pay no attention to matches that are not captured.
Without the DOTALL flag (/s) periods match all characters other than line terminators; with that flag set periods match all characters, including line terminators.
Demo
At the demo link matches that are not captured (not comments, so disregard) are shown in blue, whereas matches that are captured (comments) are shown in green.
The regular expression can be broken down as follows.
'.*?' # match a single-quote followed by >= 0 chars, lazily,
# followed by a single-quote
| # or
".*?" # match a double-quote followed by >= 0 chars, lazily,
# followed by a double-quote
| # or
( # begin capture group 1
\/\/ # match '//'
[^\r\n]* # match >= 0 chars other than line terminators
| # or
\/\* # match '/*'
.*? # match >= 0 chars, lazily
\*\/ # match '*/'
) # end capture group 1
Here is an example of how this works. Suppose the string were as follows.
A dog "is // a\nman's" /* best */ 'friend /* so it */ is' // said
The regex engine performs the following steps.
Fail to match A.
Fail to match after A, then fail to match d, o, g and .
Match but do not capture "is // a\nman's".1
Fail to match .
Match and capture the comment /* best */.
Fail to match .
Match but do not capture 'friend /* so it */ is'.
Fail to match .
Match and capture the comment // said
1. After this match the regex engine's string pointer is between the (last) double-quote just matched and the following space.
This returns what you're looking for in the example, let me know if you find any edge cases. You'll have to post-process the matches based on whether it's a comment or quoted string.
(?:(?:(\/)(\*)|(["'])).*?(?:\2\1|\3))|(?:\/\/[^\n]+)
https://regex101.com/r/uqx1cJ/1
I'am looking to exclude matches that contain a specific word or phrase. For example, how could I match only lines 1 and 3? the \b word boundary does not work intuitively like I expected.
foo.js # match
foo_test.js # do not match
foo.ts # match
fun_tset.js # match
fun_tset_test.ts # do not match
UPDATE
What I want to exclude is strings ending explicitly with _test before the extension. At first I had something like [^_test], but that also excludes any combination of those characters (like line 3).
Regex: ^(?!.*_test\.).*$
Working examples: https://regex101.com/r/HdGom7/1
Why it works: uses negative lookahead to check if _test. exists somewhere in the string, and if so doesn't match it.
Adding to #pretzelhammer's answer, it looks like you want to grab strings that are file names ending in ts or js:
^(?!.*_test)(.*\.[jt]s)
The expression in the first parentheses is a negative lookahead that excludes any strings with _test, the second parentheses matches any strings that end in a period, followed by [jt] (j or t), followed by s.
I am trying to write a regex expression which will capture all instances of the '#' character, except when two such characters appear in succession (essentially, an escape sequence). For example:
abd#ajk: # should be matched
abd##ajk: No matches
abd###ajk: The final # should match.
abd####ajk: No matches
This almost works with the negative lookahead expression #(?!#), except that because the second # is not consumed, the last of two # symbols will still be matched. What I think I want to do is to lookahead for an # but consume the character if it is there; otherwise, do not consume it. Is this possible?
Edit: I'm using Javascript which unfortunately rules out several good approaches :(
In JavaScript, to split strings at an unescaped #, you may actually match chunks of text that is either ## (an escaped #) and any chars other than #:
var strs = ['abd#ajk','abd##ajk','abd###ajk','abd####ajk'];
var rx = /(?:[^#]|##)+/g;
for (var s of strs) {
console.log(s, "=>", s.match(rx))
}
The regex is
/(?:[^#]|##)+/g
See its demo
Details
(?: - start of a non-capturing group that matches either of the 2 alternatives:
[^#]- any char other than#`
| - or
## - 2 #s
)+ - repeat matching 1 or more times.
The g modifier finds all matching occurrences inside the input string.
Since you didn't tag a programming language to your question here is my 2 cents for Java:
(?<=(?<!#)(?:##){0,999})#(?!#)
Java doesn't support infinite lookbehinds but bounded so here I explicitly specified max of even occurrences of #: 999.
JavsScript
Lookbehinds in JavaScript are not implemented and supported by many browsers yet. If you are trying to do this in JS then this would be your working solution:
Method 1
((?:[^#]*(?:##)+[^#]*)+)|#
(?:[^#]*(?:##)+[^#]*)+ Match ## occurrences and all its leading / trailing characters
|# Or a single #
JS Code:
str.split(/((?:[^#]*(?:##)+[^#]*)+)|#/).filter(Boolean);
Method 2 (Recommended)
Or if you don't have problem with using match() this is much more cleaner and of course faster:
(?:[^#]*(?:##)+[^#]*)+|[^#]+
JS Code:
console.log(
"aaaa#######bbb#aa###cccc##ddddd#".match(/(?:[^#]*(?:##)+[^#]*)+|[^#]+/g)
);
filter: function(t){ return /^#\w+/.test(t.tweet_raw_text); },
If this JS returns tweets that start with an # symbol, how to do return tweets with a specific hash tag, or word in them?
Everything I try just breaks it! It originates from this JS:
http://tweet.seaofclouds.com/
First let's break down the regular expression you have to see how it works.
/^#\w+/ - The slashes (/) at the beginning and end are just delimiters that tell JavaScript that this is a regular expression.
^ - matches the beginning of a string.
# - matches the literal # symbol.
\w - matches any alphanumeric character including underscore (short for [a-zA-Z0-9_]).
+ - is short for {1,}. Matches the previous character or expression (\w) one or more times.
That's how you match a tweet that starts with the # symbol. To match a tweet that contains a specific hashtag, you can replace the regular expression above with the specific hashtag you're trying to match.
For example, /#StackOverflow/.test(t.tweet_raw_text); will match a tweet that contains the exact hashtag #StackOverflow. That's a case-sensitive pattern though, so it wouldn't match the hashtag #stackoverflow. To make a JavaScript regular expression case insensitive, just add the i modifier after the closing delimeter like so: /#StackOverflow/i.
Thank your the above reply - a good lesson in reg expressions.
I also got round the problem with this code:
filter: function(t){ if (t.tweet_raw_text.indexOf("#EF1") !== -1; },
I'm trying to exclude some internal IP addresses and some internal IP address formats from viewing certain logos and links in the site.I have multiple range of IP addresses(sample given below). Is it possible to write a regex that could match all the IP addresses in the list below using javascript?
10.X.X.X
12.122.X.X
12.211.X.X
64.X.X.X
64.23.X.X
74.23.211.92
and 10 more
Quote the periods, replace the X's with \d+, and join them all together with pipes:
const allowedIPpatterns = [
"10.X.X.X",
"12.122.X.X",
"12.211.X.X",
"64.X.X.X",
"64.23.X.X",
"74.23.211.92" //, etc.
];
const allowedRegexStr = '^(?:' +
allowedIPpatterns.
join('|').
replace(/\./g, '\\.').
replace(/X/g, '\\d+') +
')$';
const allowedRegexp = new RegExp(allowedRegexStr);
Then you're all set:
'10.1.2.3'.match(allowedRegexp) // => ['10.1.2.3']
'100.1.2.3'.match(allowedRegexp) // => null
How it works:
First, we have to turn the individual IP patterns into regular expressions matching their intent. One regular expression for "all IPs of the form '12.122.X.X'" is this:
^12\.122\.\d+\.\d+$
^ means the match has to start at the beginning of the string; otherwise, 112.122.X.X IPs would also match.
12 etc: digits match themselves
\.: a period in a regex matches any character at all; we want literal periods, so we put a backslash in front.
\d: shorthand for [0-9]; matches any digit.
+: means "1 or more" - 1 or more digits, in this case.
$: similarly to ^, this means the match has to end at the end of the string.
So, we turn the IP patterns into regexes like that. For an individual pattern you could use code like this:
const regexStr = `^` + ipXpattern.
replace(/\./g, '\\.').
replace(/X/g, '\\d+') +
`$`;
Which just replaces all .s with \. and Xs with \d+ and sticks the ^ and $ on the ends.
(Note the doubled backslashes; both string parsing and regex parsing use backslashes, so wherever we want a literal one to make it past the string parser to the regular expression parser, we have to double it.)
In a regular expression, the alternation this|that matches anything that matches either this or that. So we can check for a match against all the IP's at once if we to turn the list into a single regex of the form re1|re2|re3|...|relast.
Then we can do some refactoring to make the regex matcher's job easier; in this case, since all the regexes are going to have ^...$, we can move those constraints out of the individual regexes and put them on the whole thing: ^(10\.\d+\.\d+\.\d+|12\.122\.\d+\.\d+|...)$. The parentheses keep the ^ from being only part of the first pattern and $ from being only part of the last. But since plain parentheses capture as well as group, and we don't need to capture anything, I replaced them with the non-grouping version (?:..).
And in this case we can do the global search-and-replace once on the giant string instead of individually on each pattern. So the result is the code above:
const allowedRegexStr = '^(?:' +
allowedIPpatterns.
join('|').
replace(/\./g, '\\.').
replace(/X/g, '\\d+') +
')$';
That's still just a string; we have to turn it into an actual RegExp object to do the matching:
const allowedRegexp = new RegExp(allowedRegexStr);
As written, this doesn't filter out illegal IPs - for instance, 10.1234.5678.9012 would match the first pattern. If you want to limit the individual byte values to the decimal range 0-255, you can use a more complicated regex than \d+, like this:
(?:\d{1,2}|1\d{2}|2[0-4]\d|25[0-5])
That matches "any one or two digits, or '1' followed by any two digits, or '2' followed by any of '0' through '4' followed by any digit, or '25' followed by any of '0' through '5'". Replacing the \d with that turns the full string-munging expression into this:
const allowedRegexStr = '^(?:' +
allowedIPpatterns.
join('|').
replace(/\./g, '\\.').
replace(/X/g, '(?:\\d{1,2}|1\\d{2}|2[0-4]\\d|25[0-5])') +
')$';
And makes the actual regex look much more unwieldy:
^(?:10\.(?:\d{1,2}|1\d{2}|2[0-4]\d|25[0-5])\.(?:\d{1,2}|1\d{2}|2[0-4]\d|25[0-5]).(?:\d{1,2}|1\d{2}|2[0-4]\d|25[0-5])|12\.122\....
but you don't have to look at it, just match against it. :)
You could do it in regex, but it's not going to be pretty, especially since JavaScript doesn't even support verbose regexes, which means that it has to be one humongous line of regex without any comments. Furthermore, regexes are ill-suited for matching ranges of numbers. I suspect that there are better tools for dealing with this.
Well, OK, here goes (for the samples you provided):
var myregexp = /\b(?:74\.23\.211\.92|(?:12\.(?:122|211)|64\.23)\.(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\.(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])|(?:10|64)\.(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\.(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\.(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9]))\b/g;
As a verbose ("readable") regex:
\b # start of number
(?: # Either match...
74\.23\.211\.92 # an explicit address
| # or
(?: # an address that starts with
12\.(?:122|211) # 12.122 or 12.211
| # or
64\.23 # 64.23
)
\. # .
(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\. # followed by 0..255 and a dot
(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9]) # followed by 0..255
| # or
(?:10|64) # match 10 or 64
\. # .
(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\. # followed by 0..255 and a dot
(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\. # followed by 0..255 and a dot
(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9]) # followed by 0..255
)
\b # end of number
/^(X|\d{1,3})(\.(X|\d{1,3})){3}$/ should do it.
If you don't actually need to match the "X" character you could use this:
\b(?:\d{1,3}\.){3}\d{1,3}\b
Otherwise I would use the solution cebarrett provided.
I'm not entirely sure of what you're trying to achieve here (doesn't look anyone else is either).
However, if it's validation, then here's a solution to validate an IP address that doesn't use RegEx. First, split the input string at the dot. Then using parseInt on the number, make sure it isn't higher than 255.
function ipValidator(ipAddress) {
var ipSegments = ipAddress.split('.');
for(var i=0;i<ipSegments.length;i++)
{
if(parseInt(ipSegments[i]) > 255){
return 'fail';
}
}
return 'match';
}
Running the following returns 'match':
document.write(ipValidator('10.255.255.125'));
Whereas this will return 'fail':
document.write(ipValidator('10.255.256.125'));
Here's a noted version in a jsfiddle with some examples, http://jsfiddle.net/VGp2p/2/