FOR EXAMPLE: Given a string... "1,2,3,4"
I need to be able to remove a given number and the comma after/before depending on if the match is at the end of the string or not.
remove(2) = "1,3,4"
remove(4) = "1,2,3"
Also, I'm using javascript.
As jtdubs shows, an easy way is is to use a split function to obtain an array of elements without the commas, remove the required element from the array, and then rebuild the string with a join function.
For javascript something like this might work:
function remove(array,to_remove)
{
var elements=array.split(",");
var remove_index=elements.indexOf(to_remove);
elements.splice(remove_index,1);
var result=elements.join(",");
return result;
}
var string="1,2,3,4,5";
var newstring = remove(string,"4"); // newstring will contain "1,2,3,5"
document.write(newstring+"<br>");
newstring = remove(string,"5");
document.write(newstring+"<br>"); // will contain "1,2,3,4"
You also need to consider the behavior you want if you have repeats, say the string is "1,2,2,4" and I say "remove(2)" should it remove both instances or just the first? this function will remove only the first instance.
Just use multiple substitutions.
s/^$removed,//;
s/,$removed$//;
s/,$removed,/,/;
This will be easier than trying to invent a single replacement that handles all those cases.
string input = "1,2,3,4";
List<string> parts = new List<string>(input.Split(new char[] { ',' }));
parts.RemoveAt(2);
string output = String.Join(",", parts);
Instead of using regex, I would do something like:
- split on comma
- delete the right element
- join with comma
Here is a perl script that does the job:
#!/usr/bin/perl
use 5.10.1;
use strict;
use warnings;
my $toremove = 5;
my $string = "1,2,3,4,5";
my #tmp = split/,/, $string;
#tmp = grep{ $_ != $toremove }#tmp;
$string =join',', #tmp;
say $string;
Output:
1,2,3,4
Javascript has improved since this question was posted.
I use the following regex to remove items from a csv string
let searchStr = "359";
let regex = new RegExp("^" + searchStr + ",?|," + searchStr);
csvStr = csvStr.replace(regex, "");
If the child_id is the start, middle or end, or only item it is replaced.
If the searchStr is at the start of the csvStr it and any trailing comma is replaced. Else if the searchStr is anywhere else in the csvStr it must be preceded with a comma so the searchStr and its preceding comma are replaced by an empty string.
Related
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 that looks like this, they are ids in a table:
1,2,3,4,5,6,7,8,9
If someone deletes something from the database, I will need to update the string. I know that doing this it will remove the value, but not the commas. Any idea how can I check if the id has a comma before and after so my string doesn't break?
$new_values = $original_values[0];
$new_values =~ s/$car_id//;
Result: 1,2,,4,5,6,7,8,9 using the above sample (bad). It should be 1,2,4,5,6,7,8,9.
To remove the $car_id from the string:
my $car_id = 3;
my $new_values = q{1,2,3,4,5,6,7,8,9};
$new_values = join q{,}, grep { $_ != $car_id }
split /,/, $new_values;
say $new_values;
# Prints:
# 1,2,4,5,6,7,8,9
If you already removed the id(s), and you need to remove the extra commas, reformat the string like so:
my $new_values = q{,,1,2,,4,5,6,7,8,9,,,};
$new_values = join q{,}, grep { /\d/ } split /,/, $new_values;
say $new_values;
# Prints:
# 1,2,4,5,6,7,8,9
You can use
s/^$car_id,|,$car_id\b//
Details
^ - start of string
$car_id - variable value
, - comma
| - or
, - comma
$car_id - variable value
\b - word boundary.
s/^\Q$car_id\E,|,\Q$car_id\E\b//
Another approach is to store an extra leading and trailing comma (,1,2,3,4,5,6,7,8,9,)
The main benefit is that it makes it easier to search for the id using SQL (since you can search for ,$car_id,). Same goes for editing it.
On the Perl side, you'd use
s/,\K\Q$car_id\E,// # To remove
substr($_, 1, -1) # To get actual string
Ugly way: use regex to remove the value, then simplify
$new_values = $oringa_value[0];
$new_values =~ s/$car_id//;
$new_values =~ s/,+/,/;
Nice way: split and merge
$new_values = $oringa_value[0];
my #values = split(/,/, $new_values);
my $index = 0;
$index++ until $values[$index] eq $car_id;
splice(#values, $index, 1);
$new_values = join(',', #values);
Definitely I'm not good using regular expressions but are really cool!, Now I want to be able to get only the name "table" in this string:
[schema].[table]
I want to remove the schema name, the square brackets and the dot.
so I will get only the work table
I tried this:
string output = Regex.Replace(reader["Name"].ToString(), #"[\[\.\]]", "");
So you came up with a new idea?? Here is what you can try:
string input = "[schema].[table]";
// replacing the first thing into [] with the dot with empty
string one = Regex.Replace(input, #"^\[.*?\]\.", "");
// or replacing anything before the dot with empty
// string two = Regex.Replace(input, #".*[.]", "");
try this
string strRegex = #"^\[.*?\]\.";
Regex myRegex = new Regex(strRegex, RegexOptions.None);
string strTargetString = #"[schema].[table]";
string strReplace = #"";
var result=myRegex.Replace(strTargetString, strReplace);
Console.WriteLine(result);
Why do you want to do replace if you just want to extract part of string?
string table = Regex.Match("[schema].[table]", #"\w+(?=]$)").Value;
It works even in case if you don't have schema.
I want to get an array of all the words with capital letters that are included in the string. But only if the line begins with "set".
For example:
- string "setUserId", result array("User", "Id")
- string "getUserId", result false
Without limitation about "set" RegEx look like /([A-Z][a-z]+)/
$str ='setUserId';
$rep_str = preg_replace('/^set/','',$str);
if($str != $rep_str) {
$array = preg_split('/(?<=[a-z])(?=[A-Z])/',$rep_str);
var_dump($array);
}
See it
Also your regex will also work.:
$str = 'setUserId';
if(preg_match('/^set/',$str) && preg_match_all('/([A-Z][a-z]*)/',$str,$match)) {
var_dump($match[1]);
}
See it
I need a AS3 regular expression that allows me to find/replace in strings like these:
var str1:String = "<value1 att="1"> some text</value1>";
var str2:String = "<value1 att="1" var="a"> some text and more</value1>";
var str3:String = "<value1 att="ok" var="b" def="12"> some text</value1>";
to this:
str1 = "<value1 att="1">*some text</value1>";
str2 = "<value1 att="1" var="a">**some text and more</value1>";
str3 = "<value1 att="ok" var="b" def="12">*****some text</value1>";
I want to be able to replace the spaces at the beginning (inside the > <) for other character. It shouldn't affect the number of character at the right of the spaces or the attributes in the value1 definition.
Assuming that there are no "* " sequences in the text blocks, this should work:
var s:String = "<value1 att='ok' var='b' def='12'> some text</value1>";
//find all spaces after a tag closing bracket and replace with a *
s = s.replace(/>\s/g, ">*");
//find all spaces after a * and replace it with a *
//keep doing this until no more can be found
while (s.match(/>\*+\s/g).length) {
s = s.replace(/\*\s/g, "**");
}
I can't think of a way to do it in one replace though.
I think the easiest way to accomplish what you need is to use a function in replace() expression.
var replaceMethod:Function = function (match:String, tagName:String, tagContent:String, spaces:String, targetText:String, index:int, whole:String) : String
{
trace("\t", "found", spaces.length,"spaces in tag '"+tagName+"'");
trace("\t", "matched string:", match);
// check tag name or whatever you may want
// do something with found spaces
var replacement:String = spaces.replace(" ", "*");
return "<"+tagName+" "+tagContent+">"+replacement+targetText;
}
var str1:String = '<value1 att="1"> some text</value1>';
var exp:RegExp = /<(\w+)([ >].*?)>(\s+)(some text)/gm;
trace("before:", str1);
str1 = str1.replace(exp, replaceMethod);
trace("after:", str1);
It's not performance-safe though; if you are using huge blocks of text and/or launching this routine very frequently, you may want to do something more comlicated, but optimized. One optimization technique is reducing the number of arguments of replaceMathod().
p.s. I think this can be done with one replace() expression and without using replaceMethod(). Look at positive lookaheads and noncapturing groups, may be you can figure it out. http://livedocs.adobe.com/flex/3/html/help.html?content=12_Using_Regular_Expressions_09.html