Good day. I wanna detect the url string in the <a> tag
Link
whether it matchs the pattern : ?post_type=tribe_events&p=#### (#### = 4 digits number)
I'm writing some Jquery code to detect the expression but the console is throwing the error :
Invalid regular expression: /^(?)post_type=tribe_events&p=^(d{4})/:
Invalid group
var str = $(a).attr("href");
var regexEx = /^(?)post_type=tribe_events&p=^(d{4})/;
var ok = regexEx.exec(str);
console.log(ok);
I'm not good at the regex so I'd be aprreciated if there's any help.
There are couple of issues in your regex.
You need to remove ^ from your regex which denotes start of string and in your case your string doesn't actually start from a ? and is in middle of the string.
You need to escape ? as it has special meaning in regex which is zero or one occurrence of a character.
You need to remove second ^ after p= which isn't needed
You need to write \d and not just d for representing a number.
Also you don't need to group ? and \d{4} unless you really need them.
You corrected regex becomes,
\?post_type=tribe_events&p=\d{4}
Demo
If the test is really what you want, I suppose the right syntax would be:
/^\?post_type=tribe_events&p=\d{4}/
Related
I need a regular expression for :
<<12.txt>> <<45.txt>
I have created a regular expression :
<<.+.txt>>
But this found one match in whole string but here is 2 matches:
<<12.txt>>
<<45.txt>>
if anyone have solution for this problem please help me out there
Part of the issue is that the string you've specified wouldn't match because the second > is missing in <<45.txt>.
Also, you're using the . (dot) selector, and also trying to find a period. It works, but now how you think it is.
Here's the regex you want:
var regex = /<<\d+\.txt>>/g
\d matches only numbers
\. matches an actual period
/g means global, so it won't stop at the first match
Practice Regular Expressions
https://regexr.com/43bs4
Demo
var string = "<<12.txt>> <<45.txt>>";
var regex = /<<\d+\.txt>>/g;
var matches = string.match(regex);
console.log(matches);
P.S., if you actually want to match with 1 > or 2 >>, you can with:
var regex = /<<\d+\.txt>>?/g
? optionally matches the character right before it
/<<.+.txt>>/gm
g is for global (will search through entire source)
m is for multi line search support
I have a sample format for which I want the regular expression in javascript. The format is as below.
I-KA-BGLK-ENB-V001
I am unable to try as I dont know much about the Regex Please let me know how to get it.
Even If I get the regex it will do, the javascript part I can handle it.
try this
var str = 'I-KA-BGLK-ENB-V001';
var re = /^[A-Z]-[A-Z]{2}-[A-Z]{4}-[A-Z]{3}-[A-Z]\d{3}$/;
re.test(str);// true
[A-Z] - means any uppercase letter
\d - means any digit 0-9
\d{3} - means 3 digits
[A-Z]{2} - means 2 uppercace letters
You can change if you need digits in some places.
If you dont care about lowercase or uppercase replace [A-Z] with \w
https://github.com/zeeshanu/learn-regex - lessons
Or you google "learn regex easy"
The valid regular expression for this is:
^\w-\w{2}-\w{4}-\w{3}-\w{4}$
^\w-\w{2}-\w{4}-\w{3}-\w\d{3}$
Explanation
Code
I don't wanna spoon-feed you, but the next step is to Check whether a string matches a regex in JS.
Well to match strings in the I-KA-BGLK-ENB-V001 format you can use this regex:
^[A-Z]\-[A-Z]{2}\-[A-Z]{4}\-[A-Z]{3}\-\w{4}$
You can test it in Regex101, where you can see an example of matching strings and check the meaning and the specifications for each part of it.
This
var re = /[^<a]b/;
var str = "<a>b";
console.log(str.match(re)[0]);
matches >b.
However, I don't understand why this pattern /[^<a>]b/ doesn't match anything. I want to capture only the "b".
The reason why /[^<a>]b/ doesn't do anything is that you are ignoring <, a, and > as individual characters, so rewriting it as /[^><a]b/ would do the same thing. I doubt this is what you want, though. Try the following:
var re = /<a>(b)/;
var str = "<a>b";
console.log(str.match(re)[1]);
This regex looks for a string that looks like <a>b first, but it captures the b with the parentheses. To access the b, simply use [1] when you call .match instead of [0], which would return the entire string (<a>b).
What you're using here is a match for a b preceded by any character that is not listed in the group. The syntax [^a-z+-] where the a-z+- is a range of characters (in this case, the range of the lowercase Latin letters, a plus sign and a minus sign). So, what your regex pattern matches is any b preceded by a character that is NOT < or a. Since > doesn't fall in that range, it matches it.
The range selector basically works the same as a list of characters that are seperated by OR pipes: [abcd] matches the same as (a|b|c|d). Range selectors just have an extra functionality of also matching that same string via [a-d], using a dash in between character ranges. Putting a ^ at the start of a range automatically turns this positive range selector into a negative one, so it will match anything BUT the characters in that range.
What you are looking for is a negative lookahead. Those can exclude something from matching longer strings. Those work in this format: (?!do not match) where do not match uses the normal regex syntax. In this case, you want to test if the preceding string does not match <a>, so just use:
(?!<a>)(.{3}|^.{0,2})b
That will match the b when it is either preceded by three characters that are not <a>, or by fewer characters that are at the start of the line.
PS: what you are probably looking for is the "negative lookbehind", which sadly isn't available in JavaScript regular expressions. The way that would work is (?<!<a>)b in other languages. Because JavaScript doesn't have negative lookbehinds, you'll have to use this alternative regex.
you could write a pattern to match anchor tag and then replace it with empty string
var str = "<a>b</a>";
str = str.replace(/((<a[\w\s=\[\]\'\"\-]*>)|</a>)/gi,'')
this will replace the following strings with 'b'
<a>b</a>
<a class='link-l3'>b</a>
to better get familiar with regEx patterns you may find this website very useful regExPal
Your code :
var re = /[^<a>]b/;
var str = "<a>b";
console.log(str.match(re));
Why [^<a>]b is not matching with anything ?
The meaning of [^<a>]b is any character except < or a or > then b .
Hear b is followed by > , so it will not match .
If you want to match b , then you need to give like this :
var re = /(?:[\<a\>])(b)/;
var str = "<a>b";
console.log(str.match(re)[1]);
DEMO And EXPLANATION
It's my first time using Java Script....
What does this do?
var INTEGER_SINGLE = /\d+/;
What does the forward slashes tell you? How about the backslash? d means for digit?
Thanks!
That creates a regular expression that matches one or more digits.
Anything inside / / is a regular expression. \d matches a digit, and + is the positive closure, which means one or more.
Having said that, depending on what this regex is supposed to do, you may want to change it to:
var INTEGER_SINGLE = /^\d+$/;
^ matches the beginning of the string, and $ the end. The end result would be that any strings you try to match against the regex would have to satisfy it in the string's entirety.
var INTEGER_SINGLE = /^\d+$/;
console.log(INTEGER_SINGLE.test(12)); //true
console.log(INTEGER_SINGLE.test(12.5)); //false
Of course if the regex is supposed to only match a single integer anywhere in the string, then of course it's perfect just the way it is.
I was surfing online for date validation, but didn't exactly understand the regex. Can anyone explain it? I'm confused with ?, {} and $. Why do we need them?
dateReg = /^[0,1]?\d{1}\/(([0-2]?\d{1})|([3][0,1]{1}))\/(([1]{1}[9]{1}[9]{1}\d{1})|([2-9]{1}\d{3}))$/;
? means “zero or one occurences”.
{x} (where x is a number) means “exactly x occurences”
$ means “end of line”
These are very basic regex, I recommand you to read some documentation.
^ = beginning of the string
[0,1]? = optional zero, one or comma (the comma is probably an error)
\d{1} = exactly one digit (the {1} is redundant)
\/ = a forward slash
[0-2]? = optional zero, one or two (range character class) followed by any single digit (\d{1})
OR [3] = three (character class redundant here) followed by exactly one zero, one or comma
\/ = forward slash
[1]{1}[9]{1}[9]{1}\d{1} = 199 followed by any digit
OR 2-9 followed by any 3 digits
Overall, that's a really poorly written expression. I'd suggest finding a better one, or using a real date parser.
In Javascript you could validate date by passing it to Date.Parse() function. Successful conversion to a date object means you have a valid date.
Wouldn't recommend using regex for this. Too many edge cases and code gets hard to maintain.
? means "Zero or one of the aforementioned"
{n} means "exactly n of the aforementioned"
$ is the end of the String (Thanks #Andy E)
To summarize briefly:
`?' will match 0 or 1 times the pattern group you put in front of it. In this case, it's possibly being misused and should be left out, but it all depends on just what you want to match.
`{x}' tells the regex to match the preceding pattern group exactly x times.
`$' means to match the end of the line.
Well:
^ // start of the text
$ // end of the text
X{n} // number n inside these curly parenthesis define how many exact occurrences of X
X{m,n} // between m to n occurrences of X
X? // 0 or 1 occurrence of X
\d // any digits 0-9
For more help about Javascript date validation please see: Regular Expression to only grab date