Develop Reference

Is there a regex to replace all occurences except for the first one?

I already tried to use this for above mentioned intention
var str = "48abc5,2d25.,ft87";
str = str.replace(/[^\d(,.)?]/g, '');
console.log(str);
I expected the output would be 485,225
because of the 0-1 condition through the question mark.
However my output is 485,225.,87
Simply my final approach is to have a number seperated by comma or a dot.
Following pattern would fit my intention:
{1-9}+{0-9)?{, | . }{1-9}*
Would love to hear your solutions.

Inside character classes, all chars are literal, except for ^, \, [ and -. So, you cannot add ? there and expect it to behave as a quantifier.
You need
var str = "48abc5,2d25.,ft87";
str = str.replace(/[^\d,.]+/g, '').replace(/^([^.,]*(?:[.,][^.,]*)?).*/, '$1').replace(/^0+/, "");
console.log(str);
The .replace(/[^\d,.]+/g, '') part removes all chars other than digits, dots and commas.
The .replace(/^([^.,]*(?:[.,][^.,]*)?).*/, '$1') part keeps the first steak of digits and optionally a second streak of digits after the first . or ,.
The .replace(/^0+/, "") part removes one or more 0 digits at the beginning of the string.
Your fixed demo fiddle:
function testRegex(event){
let evt = event || window.event
console.log(evt.target.value)
document.getElementById("result").innerHTML = "Result: "+
evt.target.value.replace(/[^\d,.]+/g, '')
.replace(/^([^.,]*(?:[.,][^.,]*)?).*/, '$1')
.replace(/^0+/, "");
}
<label>Value:</label>
<input onkeyup="testRegex()" type="text"/>
<p id="result">Result:</p>

Using Regex to add spaces after punctuation but ignore instances of U.S

I am using
(/(?<=[.,])(?=[^\s])/mg,' ')
to add spaces after . and , that are not followed by spaces. I want to ignore instances of the word U.S. Could someone help do this?

You can use this regex
\b(U\.S)\b|([,.])(?=\S)
\b(U\.S)\b - Matches U.S. Since nothing is mentioned in question so i am considering word boundaries. (g1)
([.,])(?=\S) - Matches . or , followed by a non space character. (g2)
let str = 'ab.c,de'
let str2 = 'U.S xyzU.S U.S xyz.x'
const replacer = (input)=>{
return input.replace(/\b(U\.S)\b|([,.])(?=\S)/gm, function(match,g1,g2){
return g1 ? g1 : g2+' '
})
}
console.log(replacer(str))
console.log(replacer(str2))

A regex for removing certain characters only if there is a space character on either side

I have a Javascript string:
var myString= "word = another : more new: one = two";
I am trying to figure out a regex that would produce this:
var myString= "word another more new: one two";
So when the pattern of a space followed by a = sign then followed by another space would result in the = sign being removed.
Likewise for the : character as well.
If the = character or the : character are removed that is fine or if those characters are replaced by a space character that is fine as well.
In summary to replace multiple occurrences of an = or a : if and only if they
surrounded by a space character.
Whichever regex is easier to write.

Not with javascript... but you get the idea:
echo "word = another : more new: one = two" | sed 's/ [:=] / /g'
returns the desired string:
word another more new: one two
Explanation: the expression / [:=] / finds all "space followed by either colon or equals sign followed by space" and replaces with "space".

//save the appropriate RegEx in the variable re
//It looks for a space followed by either a colon or equals sign
// followed by another space
let re = /(\s(=|:)\s)/g;
//load test string into variable string
let string = "word = another : more new: one = two";
//parse the string and replace any matches with a space
let parsed_string = string.replace(re, " ");
//show result in the DOM
document.body.textContent = string + " => " + parsed_string;

Javascript - How to join two capitalize first letter of word scripts

I have an Acrobat form with some text fields with multiline on. My goal is to convert to uppercase the first letter of any sentence (look for dots) and also the first letter of any new line (after return has been pressed).
I can run each transformation separately, but do not know how to run them together.
To capitalize sentences I use the following code as custom convalidation :
// make an array split at dot
var aInput = event.value.split(". ");
var sCharacter = '';
var sWord='';
// for each element of word array, capitalize the first letter
for(i = 0; i <aInput.length; i++)
{
aInput[i] = aInput[i].substr(0, 1).toUpperCase() + aInput[i].substr(1) .toLowerCase();
}
// rebuild input string with modified words with dots
event.value = aInput.join('. ');
To capitalize new lines I replace ". " with "\r".
Thanks in advance for any help.

You can get the first character of each sentence with RegExp :
event.value = event.value.replace(/.+?[\.\?\!](\s|$)/g, function (txt) {
return txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase();
});
Demo : http://jsfiddle.net/00kzc370/
Regular Expression explained :
/.+?[\.\?\!](\s|$)/g is a regular expression.
.+?[\.\?\!](\s|$) is a pattern (to be used in a search) that match sentences ended by ., ? or ! and followed by a whitespace character.
g is a modifier. (Perform a global match (find all matches rather than stopping after the first match)).
Source : http://www.w3schools.com/jsref/jsref_obj_regexp.asp

Regular Expression: Any character that is not a letter or number

I need a regular expression that will match any character that is not a letter or a number. Once found I want to replace it with a blank space.

To match anything other than letter or number you could try this:
[^a-zA-Z0-9]
And to replace:
var str = 'dfj,dsf7lfsd .sdklfj';
str = str.replace(/[^A-Za-z0-9]/g, ' ');

This regular expression matches anything that isn't a letter, digit, or an underscore (_) character.
\W
For example in JavaScript:
"(,,#,£,() asdf 345345".replace(/\W/g, ' '); // Output: " asdf 345345"

You are looking for:
var yourVar = '1324567890abc§$)%';
yourVar = yourVar.replace(/[^a-zA-Z0-9]/g, ' ');
This replaces all non-alphanumeric characters with a space.
The "g" on the end replaces all occurrences.
Instead of specifying a-z (lowercase) and A-Z (uppercase) you can also use the in-case-sensitive option: /[^a-z0-9]/gi.

This is way way too late, but since there is no accepted answer I'd like to provide what I think is the simplest one: \D - matches all non digit characters.
var x = "123 235-25%";
x.replace(/\D/g, '');
Results in x: "12323525"
See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions

Match letters only /[A-Z]/ig
Match anything not letters /[^A-Z]/ig
Match number only /[0-9]/g or /\d+/g
Match anything not number /[^0-9]/g or /\D+/g
Match anything not number or letter /[^A-Z0-9]/ig
There are other possible patterns

try doing str.replace(/[^\w]/);
It will replace all the non-alphabets and numbers from your string!
Edit 1: str.replace(/[^\w]/g, ' ')

Just for others to see:
someString.replaceAll("([^\\p{L}\\p{N}])", " ");
will remove any non-letter and non-number unicode characters.
Source

To match anything other than letter or number or letter with diacritics like é you could try this:
[^\wÀ-úÀ-ÿ]
And to replace:
var str = 'dfj,dsf7é#lfsd .sdklfàj1';
str = str.replace(/[^\wÀ-úÀ-ÿ]/g, '_');
Inspired by the top post with support for diacritics
source

Have you tried str = str.replace(/\W|_/g,''); it will return a string without any character and you can specify if any especial character after the pipe bar | to catch them as well.
var str = "1324567890abc§$)% John Doe #$#'.replace(/\W|_/g, ''); it will return str = 1324567890abcJohnDoe
or look for digits and letters and replace them for empty string (""):
var str = "1324567890abc§$)% John Doe #$#".replace(/\w|_/g, ''); it will return str = '§$)% #$#';

Working with unicode, best for me:
text.replace(/[^\p{L}\p{N}]+/gu, ' ');