This question already has answers here:
How do you use a variable in a regular expression?
(27 answers)
Closed 7 years ago.
I have seen several similar questions on SO, but not exactly what I'm looking for.
I want to use a variable in my regEx so that when I call it, I can easily pass in a number.
Here's the hard coded regEx:
'mywonderfullString'.match(/.{1,3}/g)
Here's what I need:
'mywonderfullString'.match(/.{1,variableHERE}/g)
So when I call the regEx, I would do something like
'mywonderfullString'.match(/.{1,3}/g)
I've seen some examples using the replace regEx, but I can't seem to my example working.
You need to use RegExp constructor in-order to include variables inside regex.
var variableHERE = '3'
alert('mywonderfullString'.match(new RegExp(".{1," + variableHERE + "}", "g")))
Related
This question already has answers here:
Is there a RegExp.escape function in JavaScript?
(18 answers)
Closed 5 years ago.
Is there any way to make something.+()[]* matching literally 'something.+()[]*'? I'm using regex builder so manual escaping is not allowed. Sure, i can add hardcoded checks if (char === '+') return '\+' but i'm looking for native solution or better way
UPD
I'm sorry. I forgot to add that matching should be in given order with moving forward but not back. So [+.] will not fit my requirements because it will match both +. and .+. I need only first case (In definition order)
You don't need to escape them if within square brackets.. I just tested and works for me, but maybe not what you are looking for?
something[.+()[]]
This question already has answers here:
How do you use a variable in a regular expression?
(27 answers)
Closed 6 years ago.
I'm using the <string>.replace(/x/g,"y") to replace all instances of a character in a string to a different character, and I get exactly what I need.
My problem is with the syntax of the pattern (i.e. /x/g) that causes issues in a small post-processor I developed for all the javascript files included in my project.
The solution to my problem can be to encapsulate the string replacement within an isolated file that would not undergo post-processing.
(What post-processing does and why I use it is not important here)
My question: Suppose I create a function Switch_All_Chars(In_Str,Old_C,New_C) that replaces all instances of Old_C by New_C in In_str returning the updated string, and it would loo like:
function Switch_All_Chars(In_Str,Old_C,New_C) {
pat = /Old_C/g ;
return In_Str.replace( pat , New_C) ;
}
This would not work because par is not properly defined. Is there a syntax that would allow the definition of the pattern using a variable?
Thanks.
Use RegExp constructor:
var pat = new RegExp(Old_C, "g")
This question already has answers here:
How do you access the matched groups in a JavaScript regular expression?
(23 answers)
Closed 6 years ago.
This isn't so much about how to achieve what is explained in the example, there are plenty of easy ways to do it. The question is WHY does the example not behave as expected?
1. If I have the following string
"#foo#bar"
2. And I'm trying to get [foo, bar] with the following regex in JavaScript
"#foo#bar".match(/(?:#)([a-zA-Z]*)/gi)
3. It returns
Array [ "#foo", "#bar" ]
Ignoring the non-capturing group (?:#)
It works as I first expected in here https://regex101.com/r/zI0wH9/1
So why is this? Do JS regexes behave somehow differently?
simply try
"#foo#bar".match(/[a-zA-Z]+/gi); //outputs ["foo", "bar"]
This question already has answers here:
JavaScript regex multiline text between two tags
(5 answers)
Closed 4 years ago.
Even if I use the m flag, javascript regex seems to isolate regex matching by lines.
Example:
"if\nend".match(/if(.*?)end/m)
=> null
I want this to match. How do I get around this?
You actually want s (a.k.a. "dotall"), not m, but javascript doesn't support that. A workaround:
"if\nend".match(/if([\s\S]*?)end/)
This question already has answers here:
Why do regex constructors need to be double escaped?
(5 answers)
Closed 4 years ago.
I'm trying to convert following expression to "new Regexp()" style:
http://jsfiddle.net/HDWBZ/
var Wyrazenie = /\btest[a-z]*/g;
I'm really confused with it and have no idea how to fix it. Below is what I've done but obviously it doesn't work.
var Wyraznie = new RegExp("\btest[a-z]*","g");
Also have a question how would it look if instead of "test" I would use variable?
You should use this instead...
new RegExp("\\btest[a-z]*", "g");
... as \b will be interpolated into a single (slashless) character when JavaScript parser works through the corresponding string literal. The solution is to escape slash itself.
DEMO: http://jsfiddle.net/HDWBZ/1/