I want to add a (variable) tag to values with regex, the pattern works fine with PHP but I have troubles implementing it into JavaScript.
The pattern is (value is the variable):
/(?!(?:[^<]+>|[^>]+<\/a>))\b(value)\b/is
I escaped the backslashes:
var str = $("#div").html();
var regex = "/(?!(?:[^<]+>|[^>]+<\\/a>))\\b(" + value + ")\\b/is";
$("#div").html(str.replace(regex, "" + value + ""));
But this seem not to be right, I logged the pattern and its exactly what it should be.
Any ideas?
To create the regex from a string, you have to use JavaScript's RegExp object.
If you also want to match/replace more than one time, then you must add the g (global match) flag. Here's an example:
var stringToGoIntoTheRegex = "abc";
var regex = new RegExp("#" + stringToGoIntoTheRegex + "#", "g");
// at this point, the line above is the same as: var regex = /#abc#/g;
var input = "Hello this is #abc# some #abc# stuff.";
var output = input.replace(regex, "!!");
alert(output); // Hello this is !! some !! stuff.
JSFiddle demo here.
In the general case, escape the string before using as regex:
Not every string is a valid regex, though: there are some speciall characters, like ( or [. To work around this issue, simply escape the string before turning it into a regex. A utility function for that goes in the sample below:
function escapeRegExp(stringToGoIntoTheRegex) {
return stringToGoIntoTheRegex.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&');
}
var stringToGoIntoTheRegex = escapeRegExp("abc"); // this is the only change from above
var regex = new RegExp("#" + stringToGoIntoTheRegex + "#", "g");
// at this point, the line above is the same as: var regex = /#abc#/g;
var input = "Hello this is #abc# some #abc# stuff.";
var output = input.replace(regex, "!!");
alert(output); // Hello this is !! some !! stuff.
JSFiddle demo here.
Note: the regex in the question uses the s modifier, which didn't exist at the time of the question, but does exist -- a s (dotall) flag/modifier in JavaScript -- today.
If you are trying to use a variable value in the expression, you must use the RegExp "constructor".
var regex = "(?!(?:[^<]+>|[^>]+<\/a>))\b(" + value + ")\b";
new RegExp(regex, "is")
I found I had to double slash the \b to get it working. For example to remove "1x" words from a string using a variable, I needed to use:
str = "1x";
var regex = new RegExp("\\b"+str+"\\b","g"); // same as inv.replace(/\b1x\b/g, "")
inv=inv.replace(regex, "");
You don't need the " to define a regular expression so just:
var regex = /(?!(?:[^<]+>|[^>]+<\/a>))\b(value)\b/is; // this is valid syntax
If value is a variable and you want a dynamic regular expression then you can't use this notation; use the alternative notation.
String.replace also accepts strings as input, so you can do "fox".replace("fox", "bear");
Alternative:
var regex = new RegExp("/(?!(?:[^<]+>|[^>]+<\/a>))\b(value)\b/", "is");
var regex = new RegExp("/(?!(?:[^<]+>|[^>]+<\/a>))\b(" + value + ")\b/", "is");
var regex = new RegExp("/(?!(?:[^<]+>|[^>]+<\/a>))\b(.*?)\b/", "is");
Keep in mind that if value contains regular expressions characters like (, [ and ? you will need to escape them.
I found this thread useful - so I thought I would add the answer to my own problem.
I wanted to edit a database configuration file (datastax cassandra) from a node application in javascript and for one of the settings in the file I needed to match on a string and then replace the line following it.
This was my solution.
dse_cassandra_yaml='/etc/dse/cassandra/cassandra.yaml'
// a) find the searchString and grab all text on the following line to it
// b) replace all next line text with a newString supplied to function
// note - leaves searchString text untouched
function replaceStringNextLine(file, searchString, newString) {
fs.readFile(file, 'utf-8', function(err, data){
if (err) throw err;
// need to use double escape '\\' when putting regex in strings !
var re = "\\s+(\\-\\s(.*)?)(?:\\s|$)";
var myRegExp = new RegExp(searchString + re, "g");
var match = myRegExp.exec(data);
var replaceThis = match[1];
var writeString = data.replace(replaceThis, newString);
fs.writeFile(file, writeString, 'utf-8', function (err) {
if (err) throw err;
console.log(file + ' updated');
});
});
}
searchString = "data_file_directories:"
newString = "- /mnt/cassandra/data"
replaceStringNextLine(dse_cassandra_yaml, searchString, newString );
After running, it will change the existing data directory setting to the new one:
config file before:
data_file_directories:
- /var/lib/cassandra/data
config file after:
data_file_directories:
- /mnt/cassandra/data
Much easier way: use template literals.
var variable = 'foo'
var expression = `.*${variable}.*`
var re = new RegExp(expression, 'g')
re.test('fdjklsffoodjkslfd') // true
re.test('fdjklsfdjkslfd') // false
Using string variable(s) content as part of a more complex composed regex expression (es6|ts)
This example will replace all urls using my-domain.com to my-other-domain (both are variables).
You can do dynamic regexs by combining string values and other regex expressions within a raw string template. Using String.raw will prevent javascript from escaping any character within your string values.
// Strings with some data
const domainStr = 'my-domain.com'
const newDomain = 'my-other-domain.com'
// Make sure your string is regex friendly
// This will replace dots for '\'.
const regexUrl = /\./gm;
const substr = `\\\.`;
const domain = domainStr.replace(regexUrl, substr);
// domain is a regex friendly string: 'my-domain\.com'
console.log('Regex expresion for domain', domain)
// HERE!!! You can 'assemble a complex regex using string pieces.
const re = new RegExp( String.raw `([\'|\"]https:\/\/)(${domain})(\S+[\'|\"])`, 'gm');
// now I'll use the regex expression groups to replace the domain
const domainSubst = `$1${newDomain}$3`;
// const page contains all the html text
const result = page.replace(re, domainSubst);
note: Don't forget to use regex101.com to create, test and export REGEX code.
var string = "Hi welcome to stack overflow"
var toSearch = "stack"
//case insensitive search
var result = string.search(new RegExp(toSearch, "i")) > 0 ? 'Matched' : 'notMatched'
https://jsfiddle.net/9f0mb6Lz/
Hope this helps
I have a string right here :
const text = "12-100 12-199 12-300 12-999 12-666coucou 12-555 1-678 12c-666 plop12-100 12-199 12-300 12-999 12-666"
And 2 regex expressions :
const regex1 = /(?<=coucou).*(?=plop)/g
const regex2 = /\d{1,2}-\d{2,3}/g
I just want to match 12-555 & 1-678 with a single RegExp.
How Can I replace this .* in the first expression please?
Thank you in advance for your answers and explanations!
You can use
const regex = /(?<=coucou.*)\d{1,2}-\d{2,3}(?=.*plop)/g
See the regex demo.
JavaScript demo below:
const text = "12-100 12-199 12-300 12-999 12-666coucou 12-555 1-678 12c-666 plop12-100 12-199 12-300 12-999 12-666"
const regex = /(?<=coucou.*)\d{1,2}-\d{2,3}(?=.*plop)/g
console.log(text.match(regex));
I have the following input string: val s = 19860803 000000
I want to convert it to 1986/08/03
I tried this s.split(" ").head, but this is not complete
is there any elegant scala coding way with regex to get the expected result ?
You can use a date like pattern using 3 capture groups, and match the following space and the 6 digits.
In the replacement use the 3 groups in the replacement with the forward slashes.
val s = "19860803 000000"
val result = s.replaceAll("^(\\d{4})(\\d{2})(\\d{2})\\h\\d{6}$", "$1/$2/$3")
Output
result: String = 1986/08/03
i haven't tested this, but i think the following will work
val expr = raw"(\d{4})(\d{2})(\d{2}) (.*)".r
val formatted = "19860803 000000" match {
case expr(year,month,day,_) =>. s"$year/$month/$day"
}
scala docs have a lot of good info
https://www.scala-lang.org/api/2.13.6/scala/util/matching/Regex.html
An alternative, without a regular expression, by using slice and take.
val s = "19860803 000000"
val year = s.take(4)
val month = s.slice(4,6)
val day = s.slice(6,8)
val result = s"$year/$month/$day"
Or as a one liner
val result = Seq(s.take(4), s.slice(4,6), s.slice(6,8)).mkString("/")
I would like to remove all of the lines containing 3 or more same characters in a row.
INPUT:
colaZAAA
colaZBBB
colaZAAB
OUTPUT
colaZAAB
Thank you for your answers.
Here, we would be most likely adding two backrefereces to find those with repeating three chars, with an expression such as:
.+(.)\1\1
Demo
Test
const regex = /.+(.)\1\1/gm;
const str = `colaZAAA
colaZBBB
CCCcolaZBBB
colaZAAB`;
const subst = ``;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
RegEx Circuit
jex.im visualizes regular expressions:
If I am doing this it is working fine:
val string = "somestring;userid=someidT;otherstuffs"
var pattern = """[;?&]userid=([^;&]+)?(;|&|$)""".r
val result = pattern.findFirstMatchIn(string).get;
But I am getting an error when I am doing this
val string = "somestring;userid=someidT;otherstuffs"
val id_name = "userid"
var pattern = """[;?&]""" + id_name + """=([^;&]+)?(;|&|$)""".r
val result = pattern.findFirstMatchIn(string).get;
This is the error:
error: value findFirstMatchIn is not a member of String
You may use an interpolated string literal and use a bit simpler regex:
val string = "somestring;userid=someidT;otherstuffs"
val id_name = "userid"
var pattern = s"[;?&]${id_name}=([^;&]*)".r
val result = pattern.findFirstMatchIn(string).get.group(1)
println(result)
// => someidT
See the Scala demo.
The [;?&]$id_name=([^;&]*) pattern finds ;, ? or & and then userId (since ${id_name} is interpolated) and then = is matched and then any 0+ chars other than ; and & are captured into Group 1 that is returned.
NOTE: if you want to use a $ as an end of string anchor in the interpolated string literal use $$.
Also, remember to Regex.quote("pattern") if the variable may contain special regex operators like (, ), [, etc. See Scala: regex, escape string.
Add parenthesis around the string so that regex is made after the string has been constructed instead of the other way around:
var pattern = ("[;?&]" + id_name + "=([^;&]+)?(;|&|$)").r
// pattern: scala.util.matching.Regex = [;?&]userid=([^;&]+)?(;|&|$)
val result = pattern.findFirstMatchIn(string).get;
// result: scala.util.matching.Regex.Match = ;userid=someidT;