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How can I split a string in JavaScript after the first space after 15 characters?

I have read the solution on this post How do I split a string at a space after a certain number of characters in javascript?
And it works to a certain point. But what I am trying to achieve is slightly different.
I have a user input which has a 40 character limit. I am taking that input and displaying it on the screen. However, I need to split the input at around 20 characters and then insert the remainder on the next line. And it is only allowed to go on 2 lines max.
UPDATE:: I should also mention here that as well as displaying the text on the front end, we also need to pass the string to our backend. But instead of sending it with the <br/>, we need to insert \n to force the new line in our backend system.
Ultimately, each line cannot be over 20 characters. However, it needs to be dynamic, so that if the user inputs a string that is 30 characters, but the space comes before the 20th character, how can I adjust it so that it splits at a space before the 20th character? - I hope that makes sense.
For example
TEXT12345 STRING46789
Should appear like this
TEXT12345
STRING46789
but, also the following
TEXT STRING ABCDEF
NEW LINE HERE
Each line needs to be a maximum of 20 characters and I can't force hyphenation.
The below code is what I have done, but it doesn't work well as I often get 'undefined' before the space. Plus, its not dynamically looking for a space before the 20 character limit
Child1Name.keyup(function(e) {
var stringValue = Child1Name.val();
if (stringValue.length > 19) {
let [firstLine, secondLine] = stringValue.replace(/.{20}\S*\s+/g, "$&#").split(/\s+#/)
previewChild1Name.html(firstLine + "<br/>" + secondLine);
}else{
previewChild1Name.text(stringValue);
}
});
Any help here would be greatly appreciated.

You can write a function like below. First split your string with space and loop over it to append the word. If after appending a new word it surpasses the length then add existing word to arr and clear the current string.
Try the code below.
function getSplittedString(s, length) {
let arr = [];
let str = '';
s.split(' ').forEach(x => {
if (str !== '' && (str + ' ' + x).length > length) {
arr.push(str);
str = '';
}
str = (str + ' ' + x).trim();
});
if (str !== '') {
arr.push(str);
}
return arr.join('<br/>')
}
console.log(getSplittedString('TEXT12345 STRING46789', 20));

from what i have seen and found on this site:
mdn website
You can use split(on strings) like this on stringvalue(should be the entire string);
var stringvalue = 'TEXT12345 STRING46789';
var words = str.split(' '); // what charater need to cut the string
console.log(words[0]);
// expected output: "TEXT12345"
Sorry for the rushing the answer, kinda busy rn Hope this helps.

How to remove a specific character from a string and put it back later when needed

For example
let myString = "This is my string";
let replacedString = myString.replace(/\ /g, "") //Thisismystring
Now that all the whitespaces have been removed, how do I put them back in the exact position?
Additionally, let's suppose the replaced string undergoes some change and becomes
let myChangedString = "(T)(h)(i)(s)(i)(s)(m)(y)(s)(t)(r)(i)(n)(g)";
Now I want to put the whitespaces back where they used to be i.e after (s) and before (i), after (s) and before (m), after (y) before (s)
I've spent a couple of hours on this and been stuck in the same position, any form of help would be greatly appreciated.
EDIT: Solved, thank you very much.

The trick here is to replace the spaces with another character - rather than just removing the space. That way - its a simple matter to replace the added character with a space to return the spaces to where they started. When I do this - I always use the tilde character "~" since it is easily recognisable as well as unlikely to actually be used in a string.
I have added a few variations / modifications as well as the example you have provided with every character being wrapped in parentheses - just note that you will need to escape these when replaceing the (~) for the " " space character.
let myString = "This is my string";
let replacedString = myString.replace(/\ /g, "~");
console.log(replacedString);//This~is~my~string
let modifiedString = replacedString.replace(/my/g, "your");
console.log(modifiedString);//This~is~your~string
let spacedString = modifiedString.replace(/~/g, " ");
console.log(spacedString);//This is your string
// using your example of wrapping each character in parentheses
let myChangedString = "(" + modifiedString.split('').join(")(") + ")";
console.log(myChangedString); //(T)(h)(i)(s)(~)(i)(s)(~)(y)(o)(u)(r)(~)(s)(t)(r)(i)(n)(g)
let mySpacedString = myChangedString.replace(/\(~\)/g, " ");
console.log(mySpacedString); //(T)(h)(i)(s) (i)(s) (y)(o)(u)(r) (s)(t)(r)(i)(n)(g)

Why not replace only the parts you need to be replaced?
For example search for word character and replace with the wanted parts.
console.log("This is my string".replace(/\w/g, '($&)'));

Better you just transform your original array. Loop through array and modify the char is not empty.
let myString = "This is my string";
let chars = [...myString].map(item => item !== ' ' ? '(' + item + ')': item)
console.log(chars.join(''))

Are you looking for this...
var result = "thisismystring".replace(/^(.{4})(.{2})(.{2})(.*)$/, "$1 $2 $3 $4");
alert(result);

Remove punctuation, retain spaces, toLowerCase, add dashes succinctly

I need to do the following to a string:
Remove any punctuation (but retain spaces) (can include removal of foreign chars)
Add dashes instead of spaces
toLowercase
I'd like to be able to do this as succinctly as possible, so on one line for example.
At the moment I have:
const ele = str.replace(/[^\w\s]/, '').replace(/\s+/g, '-').toLowerCase();
Few problems I'm having. Firstly the line above is syntactically incorrect. I think it's a problem with /[^\w\s] but I am not sure what I've done wrong.
Secondly I wonder if it is possible to write a regex statement that removes the punctuation AND converts spaces to dashes?
And example of what I want to change:
Where to? = where-to
Destination(s) = destinations
Travel dates?: = travel-dates
EDIT: I have updated the missing / from the first regex replace. I am finding that Destination(s) is becoming destinations) which is peculiar.
Codepen: http://codepen.io/anon/pen/mAdXJm?editors=0011

You may use the following regex to only match ASCII punctuation and some symbols (source) - maybe we should remove _ from it:
var punct = /[!"#$%&'()*+,.\/:;<=>?#\[\\\]^`{|}~-]+/g;
or a more contracted one since some of these symbols appear in the ASCII table as consecutive chars:
var punct = /[!-\/:-#\[-^`{-~]+/g;
You may chain 2 regex replacements.
var punct = /[!"#$%&'()*+,.\/:;<=>?#\[\\\]^`{|}~-]+/g;
var s = "Where to?"; // = where-to
console.log(s.replace(punct, '').replace(/\s+/, '-').toLowerCase());
s = "Destination(s)"; // = destinations
console.log(s.replace(punct, '').replace(/\s+/, '-').toLowerCase());
console.log(s.replace(punct, '').replace(/\s+/, '-').toLowerCase());
Or use an anonymous method inside the replace with arrow functions (less compatibility, but succint):
var s="Travel dates?:"; // = travel-dates
var o=/([!-\/:-#\[-^`{-~]+)|\s+/g;
console.log(s.replace(o,(m,g)=>g?'':'-').toLowerCase());
Note you may also use XRegExp to match any Unicode punctuation with \pP construct.

Wiktor touched on the subject, but my first thought was an anonymous function using the regex /(\s+)|([\W])/g like this:
var inputs = ['Where to?', 'Destination(s)', 'Travel dates?:'],
res,
idx;
for( idx=0; idx<inputs.length; idx++ ) {
res = inputs[idx].replace(/(\s+)|([\W])/g, function(a, b) {return b ? '-' : '';}).toLowerCase();
document.getElementById('output').innerHTML += '"' + inputs[idx] + '" -> "'
+ res + '"<br/>';
}
<!DOCTYPE html>
<html>
<body>
<p id='output'></p>
</body>
</html>
The regex captures either white space (1+) or a non-word characters. If the first is true the anonymous function returns -, otherwise an empty string.

Remove (n)th space from string in JavaScript

I am trying to remove some spaces from a few dynamically generated strings. Which space I remove depends on the length of the string. The strings change all the time so in order to know how many spaces there are, I iterate over the string and increment a variable every time the iteration encounters a space. I can already remove all of a specific type of character with str.replace(' ',''); where 'str' is the name of my string, but I only need to remove a specific occurrence of a space, not all the spaces. So let's say my string is
var str = "Hello, this is a test.";
How can I remove ONLY the space after the word "is"? (Assuming that the next string will be different so I can't just write str.replace('is ','is'); because the word "is" might not be in the next string).
I checked documentation on .replace, but there are no other parameters that it accepts so I can't tell it just to replace the nth instance of a space.

If you want to go by indexes of the spaces:
var str = 'Hello, this is a test.';
function replace(str, indexes){
return str.split(' ').reduce(function(prev, curr, i){
var separator = ~indexes.indexOf(i) ? '' : ' ';
return prev + separator + curr;
});
}
console.log(replace(str, [2,3]));
http://jsfiddle.net/96Lvpcew/1/

As it is easy for you to get the index of the space (as you are iterating over the string) , you can create a new string without the space by doing:
str = str.substr(0, index)+ str.substr(index);
where index is the index of the space you want to remove.

I came up with this for unknown indices
function removeNthSpace(str, n) {
var spacelessArray = str.split(' ');
return spacelessArray
.slice(0, n - 1) // left prefix part may be '', saves spaces
.concat([spacelessArray.slice(n - 1, n + 1).join('')]) // middle part: the one without the space
.concat(spacelessArray.slice(n + 1)).join(' '); // right part, saves spaces
}

Do you know which space you want to remove because of word count or chars count?
If char count, you can Rafaels Cardoso's answer,
If word count you can split them with space and join however you want:
var wordArray = str.split(" ");
var newStr = "";
wordIndex = 3; // or whatever you want
for (i; i<wordArray.length; i++) {
newStr+=wordArray[i];
if (i!=wordIndex) {
newStr+=' ';
}
}

I think your best bet is to split the string into an array based on placement of spaces in the string, splice off the space you don't want, and rejoin the array into a string.
Check this out:
var x = "Hello, this is a test.";
var n = 3; // we want to remove the third space
var arr = x.split(/([ ])/); // copy to an array based on space placement
// arr: ["Hello,"," ","this"," ","is"," ","a"," ","test."]
arr.splice(n*2-1,1); // Remove the third space
x = arr.join("");
alert(x); // "Hello, this isa test."
Further Notes
The first thing to note is that str.replace(' ',''); will actually only replace the first instance of a space character. String.replace() also accepts a regular expression as the first parameter, which you'll want to use for more complex replacements.
To actually replace all spaces in the string, you could do str.replace(/ /g,""); and to replace all whitespace (including spaces, tabs, and newlines), you could do str.replace(/\s/g,"");
To fiddle around with different regular expressions and see what they mean, I recommend using http://www.regexr.com
A lot of the functions on the JavaScript String object that seem to take strings as parameters can also take regular expressions, including .split() and .search().

How can I replace newlines/line breaks with spaces in javascript?

I have a var that contains a big list of words (millions) in this format:
var words = "
car
house
home
computer
go
went
";
I want to make a function that will replace the newline between each word with space.
So the results would something look like this:
car house home computer go went

You can use the .replace() function:
words = words.replace(/\n/g, " ");
Note that you need the g flag on the regular expression to get replace to replace all the newlines with a space rather than just the first one.
Also, note that you have to assign the result of the .replace() to a variable because it returns a new string. It does not modify the existing string. Strings in Javascript are immutable (they aren't directly modified) so any modification operation on a string like .slice(), .concat(), .replace(), etc... returns a new string.
let words = "a\nb\nc\nd\ne";
console.log("Before:");
console.log(words);
words = words.replace(/\n/g, " ");
console.log("After:");
console.log(words);

In case there are multiple line breaks (newline symbols) and if there can be both \r or \n, and you need to replace all subsequent linebreaks with one space, use
var new_words = words.replace(/[\r\n]+/g," ");
See regex demo
To match all Unicode line break characters and replace/remove them, add \x0B\x0C\u0085\u2028\u2029 to the above regex:
/[\r\n\x0B\x0C\u0085\u2028\u2029]+/g
The /[\r\n\x0B\x0C\u0085\u2028\u2029]+/g means:
[ - start of a positive character class matching any single char defined inside it:
\r - (\x0D) - \n] - a carriage return (CR)
\n - (\x0A) - a line feed character (LF)
\x0B - a line tabulation (LT)
\x0C - form feed (FF)
\u0085 - next line (NEL)
\u2028 - line separator (LS)
\u2029 - paragraph separator (PS)
] - end of the character class
+ - a quantifier that makes the regex engine match the previous atom (the character class here) one or more times (consecutive linebreaks are matched)
/g - find and replace all occurrences in the provided string.
var words = "car\r\n\r\nhouse\nhome\rcomputer\ngo\n\nwent";
document.body.innerHTML = "<pre>OLD:\n" + words + "</pre>";
var new_words = words.replace(/[\r\n\x0B\x0C\u0085\u2028\u2029]+/g," ");
document.body.innerHTML += "<pre>NEW:\n" + new_words + "</pre>";

Code : (FIXED)
var new_words = words.replace(/\n/g," ");

Some simple solution would look like
words.replace(/(\n)/g," ");

No need for global regex, use replaceAll instead of replace
myString.replaceAll('\n', ' ')

const words = `He had
concluded that pigs
must be able
to fly in Hog Heaven.
`
document.body.innerHTML = "<pre>without-Trim-And-Remove:\n" + words + "</pre>";
trimAndRemoveSymbols=(text)=>{
return text.replace(/[\n]+/g, '').trim();
}
document.body.innerHTML += "<pre>Trim-And-Remove:\n" + trimAndRemoveSymbols(words) + "</pre>";