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JS Split multiple delimiters and get delimiters into input value

I'm asking you today for a little problem :
I have to live control capitalization/no capitalization with js on an input text field like this:
1st character of the entire string must be uppercase
1st character of each word (after space or hyphen) is free (lowercase or uppercase allowed)
All the nother characters must be lowercase
Desired Output: Grand-Father is Nice
I'm not a specialist of JS, i'm using split function, here is my code :
$('#name').on('input change',function() {
var arr1 = $(this).val().split(/[- ]/);
var result1 = "";
for (var x=0; x<arr1.length; x++)
result1+=arr1[x].substring(0,1)+arr1[x].substring(1).toLowerCase()+" ";
var res1 = result1.substring(0, result1.length-1);
var _txt = res1.charAt(0).toUpperCase() + res1.slice(1);
$('#name').val(_txt);
});
The script works but I would like to output the real delimiter found in string, even if it's a space " " or hyphen "-". Actually i can show only space. How can i solve it ?
Actual output: Grand Father is Nice
Any help would be appreciated.
Thank you!

User String.replace() with a RegExp and a callback.
If you know what are your delimiters, you can search for all characters that are no the delimiters, and format them:
var input = 'ègrand-Father is NièCe';
var d = '[^\s\-]'; // not space or dash
var result = input.replace(new RegExp('('+ d +')(' + d + '+)', 'g'), function(m, p1, p2, i) {
var end = p2.toLowerCase();
var start = i === 0 ? p1.toUpperCase() : p1;
return start + end;
});
console.log(result);
If the target browsers support it (Chrome does) or you use a transpiler, such as Babel (plugin), you can use Unicode property escapes in regular expressions (\p):
var input = 'ègrand-Father is NièCe';
var result = input.replace(/(\p{L})(\p{L}+)/gu, function(m, p1, p2, i) {
var end = p2.toLowerCase();
var start = i === 0 ? p1.toUpperCase() : p1;
return start + end;
});
console.log(result);

I'm not entirely sure what your aim is, but let's give it a shot.
This is how you can make all non-first letters be lowercase
let sentence = "this is wRoNg SenTEnce."
sentence.split(" ").map(word => word.charAt(0) + word.slice(1).toLowerCase()).join(" ")
This is how you can make first letter capital:
let sentence = "also Wrong sentence"
sentence.charAt(0).toUpperCase()

Regular Expression to replace variable with variable

I have some string that looks like this:
var string = popupLink(25, 'Any string')
I need to use a regular expression to change the number inside (note that this is a string inside of a larger string so I can't simply match and replace the number, it needs to match the full pattern, this is what I have so far:
var re = new RegExp(`popupLink\(${replace},\)`, 'g');
var replacement = `popupLink(${formFieldInsert.insertId},)`;
string = string.replace(re, replacement);
I can't figure out how to do the wildcard that will maintain the 'Any String' part inside of the Regular Expression.

If you are looking for a number, you should use \d. This will match all numbers.
For any string, you can use lazy searching (.*?), this will match any character until the next character is found.
In your replacement, you can use $1 to use the value of the first group between ( and ), so you don't lose the 'any string' value.
Now, you can simply do the following:
var newNumber = 15;
var newString = "var string = popupLink(25, 'Any string')".replace(/popupLink\(\d+, '(.*?)'\)/, "popupLink(" + newNumber + ", '$1')");
console.log(newString);

If you just need to change the number, just change the number:
string = string.replace(/popupLink\(\d+/, "popupLink(" + replacement);
Example:
var str = "var string = popupLink(25, 'Any string')";
var replacement = 42;
str = str.replace(/popupLink\(\d+/, "popupLink(" + replacement);
console.log(str);
If you really do have to match the full pattern, and "Any String" can literally be any string, it's much, much more work because you have to allow for quoted quotes, ) within quotes, etc. I don't think just a single JavaScript regex can do it, because of the nesting.
If we could assume no ) within the "Any String", then it's easy; we just look for a span of any character other than ) after the number:
str = str.replace(/(popupLink\()\d+([^)]*\))/, "$1" + replacement + "$2");
Example:
var str = "var string = popupLink(25, 'Any string')";
var replacement = 42;
str = str.replace(/(popupLink\()\d+([^)]*\))/, "$1" + replacement + "$2");
console.log(str);

How to concat two javascript variables and regex expression

I want to be able to concat two variables with a regular expression in the middle.
e.g.
var t1 = "Test1"
var t2 = "Test2"
var re = new RegEx(t1 + "/.*/" + t2);
So the result I want is an expression that matches this..
"Test1 this works Test2"
How do I get a result where I am able to match any text that has Test1 and Test2 on the ends?

Try this (I use nodejs):
> var t1 = "Test1"
> var t2 = "Test2"
> var re = new RegExp('^' + t1 + '.*' + t2 + '$')
> re
/^Test1.*Test2$/
> re.test("Test1 this works Test2")
true
Note
.* as stated in comments, this means any character repeated from 0 to ~
the slashes are automagically added when calling the RegExp constructor, but you can't have nested unprotected slashes delimiters
to ensure Test1 is at the beginning, i put ^ anchor, and for Test2 at the end, I added $ anchor
the regex constructor is not ReGex but RegExp (note the trailing p)

The RegExp constructor takes care of adding the forward slashes for you.
var t1 = "Test1";
var t2 = "Test2";
var re = new RegExp(t1 + ".*" + t2);
re.test("Test1 some_text Test2"); // true

You don't need regex:
var t1 = 'Test1';
var t2 = 'Test2';
var test = function(s) { return s.startsWith(t1) && s.endsWith(t2); };
console.log(test('Test1 this works Test2'));
console.log(test('Test1 this does not'));

if you know the beginning and the end you can enforce that:
var re = new RegExp("^" + t1 + ".*" + t2 + "$");

Take care that the value of the two variables do not contain any special regex characters, or transform those values to escape any special regex characters.
Of course, also make sure that the regex in between matches what you want it to :-)

Use dynamic (variable) string as regex pattern in JavaScript

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

How can I concatenate regex literals in JavaScript?

Is it possible to do something like this?
var pattern = /some regex segment/ + /* comment here */
/another segment/;
Or do I have to use new RegExp() syntax and concatenate a string? I'd prefer to use the literal as the code is both more self-evident and concise.

Here is how to create a regular expression without using the regular expression literal syntax. This lets you do arbitary string manipulation before it becomes a regular expression object:
var segment_part = "some bit of the regexp";
var pattern = new RegExp("some regex segment" + /*comment here */
segment_part + /* that was defined just now */
"another segment");
If you have two regular expression literals, you can in fact concatenate them using this technique:
var regex1 = /foo/g;
var regex2 = /bar/y;
var flags = (regex1.flags + regex2.flags).split("").sort().join("").replace(/(.)(?=.*\1)/g, "");
var regex3 = new RegExp(expression_one.source + expression_two.source, flags);
// regex3 is now /foobar/gy
It's just more wordy than just having expression one and two being literal strings instead of literal regular expressions.

Just randomly concatenating regular expressions objects can have some adverse side effects. Use the RegExp.source instead:
var r1 = /abc/g;
var r2 = /def/;
var r3 = new RegExp(r1.source + r2.source,
(r1.global ? 'g' : '')
+ (r1.ignoreCase ? 'i' : '') +
(r1.multiline ? 'm' : ''));
console.log(r3);
var m = 'test that abcdef and abcdef has a match?'.match(r3);
console.log(m);
// m should contain 2 matches
This will also give you the ability to retain the regular expression flags from a previous RegExp using the standard RegExp flags.
jsFiddle

I don't quite agree with the "eval" option.
var xxx = /abcd/;
var yyy = /efgh/;
var zzz = new RegExp(eval(xxx)+eval(yyy));
will give "//abcd//efgh//" which is not the intended result.
Using source like
var zzz = new RegExp(xxx.source+yyy.source);
will give "/abcdefgh/" and that is correct.
Logicaly there is no need to EVALUATE, you know your EXPRESSION. You just need its SOURCE or how it is written not necessarely its value. As for the flags, you just need to use the optional argument of RegExp.
In my situation, I do run in the issue of ^ and $ being used in several expression I am trying to concatenate together! Those expressions are grammar filters used accross the program. Now I wan't to use some of them together to handle the case of PREPOSITIONS.
I may have to "slice" the sources to remove the starting and ending ^( and/or )$ :)
Cheers, Alex.

Problem If the regexp contains back-matching groups like \1.
var r = /(a|b)\1/ // Matches aa, bb but nothing else.
var p = /(c|d)\1/ // Matches cc, dd but nothing else.
Then just contatenating the sources will not work. Indeed, the combination of the two is:
var rp = /(a|b)\1(c|d)\1/
rp.test("aadd") // Returns false
The solution:
First we count the number of matching groups in the first regex, Then for each back-matching token in the second, we increment it by the number of matching groups.
function concatenate(r1, r2) {
var count = function(r, str) {
return str.match(r).length;
}
var numberGroups = /([^\\]|^)(?=\((?!\?:))/g; // Home-made regexp to count groups.
var offset = count(numberGroups, r1.source);
var escapedMatch = /[\\](?:(\d+)|.)/g; // Home-made regexp for escaped literals, greedy on numbers.
var r2newSource = r2.source.replace(escapedMatch, function(match, number) { return number?"\\"+(number-0+offset):match; });
return new RegExp(r1.source+r2newSource,
(r1.global ? 'g' : '')
+ (r1.ignoreCase ? 'i' : '')
+ (r1.multiline ? 'm' : ''));
}
Test:
var rp = concatenate(r, p) // returns /(a|b)\1(c|d)\2/
rp.test("aadd") // Returns true

Providing that:
you know what you do in your regexp;
you have many regex pieces to form a pattern and they will use same flag;
you find it more readable to separate your small pattern chunks into an array;
you also want to be able to comment each part for next dev or yourself later;
you prefer to visually simplify your regex like /this/g rather than new RegExp('this', 'g');
it's ok for you to assemble the regex in an extra step rather than having it in one piece from the start;
Then you may like to write this way:
var regexParts =
[
/\b(\d+|null)\b/,// Some comments.
/\b(true|false)\b/,
/\b(new|getElementsBy(?:Tag|Class|)Name|arguments|getElementById|if|else|do|null|return|case|default|function|typeof|undefined|instanceof|this|document|window|while|for|switch|in|break|continue|length|var|(?:clear|set)(?:Timeout|Interval))(?=\W)/,
/(\$|jQuery)/,
/many more patterns/
],
regexString = regexParts.map(function(x){return x.source}).join('|'),
regexPattern = new RegExp(regexString, 'g');
you can then do something like:
string.replace(regexPattern, function()
{
var m = arguments,
Class = '';
switch(true)
{
// Numbers and 'null'.
case (Boolean)(m[1]):
m = m[1];
Class = 'number';
break;
// True or False.
case (Boolean)(m[2]):
m = m[2];
Class = 'bool';
break;
// True or False.
case (Boolean)(m[3]):
m = m[3];
Class = 'keyword';
break;
// $ or 'jQuery'.
case (Boolean)(m[4]):
m = m[4];
Class = 'dollar';
break;
// More cases...
}
return '<span class="' + Class + '">' + m + '</span>';
})
In my particular case (a code-mirror-like editor), it is much easier to perform one big regex, rather than a lot of replaces like following as each time I replace with a html tag to wrap an expression, the next pattern will be harder to target without affecting the html tag itself (and without the good lookbehind that is unfortunately not supported in javascript):
.replace(/(\b\d+|null\b)/g, '<span class="number">$1</span>')
.replace(/(\btrue|false\b)/g, '<span class="bool">$1</span>')
.replace(/\b(new|getElementsBy(?:Tag|Class|)Name|arguments|getElementById|if|else|do|null|return|case|default|function|typeof|undefined|instanceof|this|document|window|while|for|switch|in|break|continue|var|(?:clear|set)(?:Timeout|Interval))(?=\W)/g, '<span class="keyword">$1</span>')
.replace(/\$/g, '<span class="dollar">$</span>')
.replace(/([\[\](){}.:;,+\-?=])/g, '<span class="ponctuation">$1</span>')

It would be preferable to use the literal syntax as often as possible. It's shorter, more legible, and you do not need escape quotes or double-escape backlashes. From "Javascript Patterns", Stoyan Stefanov 2010.
But using New may be the only way to concatenate.
I would avoid eval. Its not safe.

You could do something like:
function concatRegex(...segments) {
return new RegExp(segments.join(''));
}
The segments would be strings (rather than regex literals) passed in as separate arguments.

You can concat regex source from both the literal and RegExp class:
var xxx = new RegExp(/abcd/);
var zzz = new RegExp(xxx.source + /efgh/.source);

Use the constructor with 2 params and avoid the problem with trailing '/':
var re_final = new RegExp("\\" + ".", "g"); // constructor can have 2 params!
console.log("...finally".replace(re_final, "!") + "\n" + re_final +
" works as expected..."); // !!!finally works as expected
// meanwhile
re_final = new RegExp("\\" + "." + "g"); // appends final '/'
console.log("... finally".replace(re_final, "!")); // ...finally
console.log(re_final, "does not work!"); // does not work

No, the literal way is not supported. You'll have to use RegExp.

the easier way to me would be concatenate the sources, ex.:
a = /\d+/
b = /\w+/
c = new RegExp(a.source + b.source)
the c value will result in:
/\d+\w+/

I prefer to use eval('your expression') because it does not add the /on each end/ that ='new RegExp' does.