Develop Reference

Extract strings between occurences of a specific character

I'm attempting to extract strings between occurences of a specific character in a larger string.
For example:
The initial string is:
var str = "http://www.google.com?hello?kitty?test";
I want to be able to store all of the substrings between the question marks as their own variables, such as "hello", "kitty" and "test".
How would I target substrings between different indexes of a specific character using either JavaScript or Regular Expressions?

You could split on ? and use slice passing 1 as the parameter value.
That would give you an array with your values. If you want to create separate variables you could for example get the value by its index var1 = parts[0]
var str = "http://www.google.com?hello?kitty?test";
var parts = str.split('?').slice(1);
console.log(parts);
var var1 = parts[0],
var2 = parts[1],
var3 = parts[2];
console.log(var1);
console.log(var2);
console.log(var3);

Quick note: that URL would be invalid. A question mark ? denotes the beginning of a query string and key/value pairs are generally provided in the form key=value and delimited with an ampersand &.
That being said, if this isn't a problem then why not split on the question mark to obtain an array of values?
var split_values = str.split('?');
//result: [ 'http://www.google.com', 'hello', 'kitty', 'test' ]
Then you could simply grab the individual values from the array, skipping the first element.

I believe this will do it:
var components = "http://www.google.com?hello?kitty?test".split("?");
components.slice(1-components.length) // Returns: [ "hello", "kitty", "test" ]

using Regular Expressions
var reg = /\?([^\?]+)/g;
var s = "http://www.google.com?hello?kitty?test";
var results = null;
while( results = reg.exec(s) ){
console.log(results[1]);
}

The general case is to use RegExp:
var regex1 = new RegExp(/\?.*?(?=\?|$)/,'g'); regex1.lastIndex=0;
str.match(regex1)
Note that this will also get you the leading ? in each clause (no look-behind regexp in Javascript).
Alternatively you can use the sticky flag and run it in a loop:
var regex1 = new RegExp(/.*?\?(.*?)(?=\?|$)/,'y'); regex1.lastIndex=0;
while(str.match(regex1)) {...}

You can take the substring starting from the first question mark, then split by question mark
const str = "http://www.google.com?hello?kitty?test";
const matches = str.substring(str.indexOf('?') + 1).split(/\?/g);
console.log(matches);

Regex matching comma delimited strings

Given any of the following strings, where operator and value are just placeholders:
"operator1(value)"
"operator1(value), operator2(value)"
"operator1(value), operator2(value), operator_n(value)"
I need to be able to match so i can get each operator and it's value as follows:
[[operator1, value]]
[[operator1, value], [operator2, value]]
[[operator1, value], [operator2, value], [operator_n, value]]
Please Note: There could be n number of operators (comma delimited) in the given string.
My current attempt will match on operator1(value) but nothing with multiple operators. See regex101 for the results.
/^(.*?)\((.*)\)$/

You should be able to do this with a single regex using the global flag.
var re= /(?:,\s*)?([^(]+?)\(([^)]+)\)/g;
var results = re.exec(str);
See the result at Regex 101: https://regex101.com/r/eC3uK3/2

Here's a pure regex answer to this question, this will work so long as your variables are always separated by a , and a space, should traverse through lines without much issue
https://regex101.com/r/eC3uK3/4
([^\(]*)(\([^, ]*\))(?:, )?(?:\n)?
Matches on:
operator1(value), operator2(value), operator_n(value),
operator1(value), operator2(value)
Explanation:
So, this sets up 2 capture groups and 2 non-capture groups.
The first capture group will match a value name until a parenthesis (by using a negated set and greedy). The second capture group will grab the parenthesis and the value name until the end of the parenthesis are found (note you can get rid of the parenthesis by escaping the outer set of parenthesis rather than the inner (Example here: https://regex101.com/r/eC3uK3/6). There's an optional ", " in a non capturing group, and an optional "\n" in another non-capturing group to handle any newline characters that you may happen across.
This should break your data out into:
'Operator1'
'(value)'
'operator2'
'(value)'
For as many as there are.

You can do this by first splitting then using a regular expression:
[
"operator1(value)",
"operator1(value), operator2(value)",
"operator1(value), operator2(value), operator_n(value)"
].forEach((str)=>{
var results = str
.split(/[,\s]+/) // split operations
.map(s=>s.match(/(\w+)\((\w+)\)/)) // extracts parts of the operations
.filter(Boolean) // ensure there's no error (in case of impure entries)
.map(s=>s.slice(1)); // make the desired result
console.log(results);
});

The following function "check" will achieve what you are looking for, if you want a string instead of an array of result, simply use the .toString() method on the array returned from the function.
function check(str) {
var myRe = /([^(,\s]*)\(([^)]*)\)/g;
var myArray;
var result = [];
while ((myArray = myRe.exec(str)) !== null) {
result.push(`[${myArray[1]}, ${myArray[2]}]`);
};
return result;
}
var check1 = check("operator1(value)");
console.log("check1", check1);
var check2 = check("operator1(value), operator2(value)");
console.log("check2", check2);
var check3 = check("operator1(value), operator2(value), operator_n(value)");
console.log("check3", check3);

This can also be done with a simple split and a for loop.
var data = "operator1(value), operator2(value), operator_n(value)",
ops = data.substring(0, data.length - 1), // Remove the last parenth from the string
arr = ops.split(/\(|\), /),
res = [], n, eN = arr.length;
for (n = 0; n < eN; n += 2) {
res.push([arr[n], arr[n + 1]]);
}
console.log(res);
The code creates a flattened array from a string, and then nests arrays of "operator"/"value" pairs to the result array. Works for older browsers too.

Javascript split to split string in 2 parts irrespective of number of spit characters present in string

I want to split a string in Javascript using split function into 2 parts.
For Example i have string:
str='123&345&678&910'
If i use the javascripts split, it split it into 4 parts.
But i need it to be in 2 parts only considering the first '&' which it encounters.
As we have in Perl split, if i use like:
($fir, $sec) = split(/&/,str,2)
it split's str into 2 parts, but javascript only gives me:
str.split(/&/, 2);
fir=123
sec=345
i want sec to be:
sec=345&678&910
How can i do it in Javascript.

var subStr = string.substring(string.indexOf('&') + 1);
View this similar question for other answers:
split string only on first instance of specified character

You can use match instead of split:
str='123&345&678&910';
splited = str.match(/^([^&]*?)&(.*)$/);
splited.shift();
console.log(splited);
output:
["123", "345&678&910"]

You can remain on the split part by using the following trick:
var str='123&345&678&910',
splitted = str.split( '&' ),
// shift() removes the first item and returns it
first = splitted.shift();
console.log( first ); // "123"
console.log( splitted.join( '&' ) ); // "345&678&910"

I wrote this function:
function splitter(mystring, mysplitter) {
var myreturn = [],
myindexplusone = mystring.indexOf(mysplitter) + 1;
if (myindexplusone) {
myreturn[0] = mystring.split(mysplitter, 1)[0];
myreturn[1] = mystring.substring(myindexplusone);
}
return myreturn;
}
var str = splitter("hello-world-this-is-a-test", "-");
console.log(str.join("<br>"));
//hello
//world-this-is-a-test​​​
The output will be either an empty array (not match) or an array with 2 elements (before the split and everything after)
Demo

I have that:
var str='123&345&678&910';
str.split('&',1).concat( str.split('&').slice(1).join('&') );
//["123", "345&678&910"]
str.split('&',2).concat( str.split('&').slice(2).join('&') );
//["123", "345", "678&910"];
for convenience:
String.prototype.mySplit = function( sep, chunks) {
chunks = chunks|=0 &&chunks>0?chunks-1:0;
return this.split( sep, chunks )
.concat(
chunks?this.split( sep ).slice( chunks ).join( sep ):[]
);
}

What about the use of split() and replace()?:
Given we have that string str='123&345&678&910' We can do
var first = str.split("&",1); //gets the first word
var second = str.replace(first[0]+"&", ""); //removes the first word and the ampersand
Please note that split() returns an array that is why getting the index with first[0] is recommended, however, without getting the index, it still worked as needed i.e first+"&".
Feel free to replace the "&" with the string you need to split with.
Hope this helps :)

Javascript split only once and ignore the rest

I am parsing some key value pairs that are separated by colons. The problem I am having is that in the value section there are colons that I want to ignore but the split function is picking them up anyway.
sample:
Name: my name
description: this string is not escaped: i hate these colons
date: a date
On the individual lines I tried this line.split(/:/, 1) but it only matched the value part of the data. Next I tried line.split(/:/, 2) but that gave me ['description', 'this string is not escaped'] and I need the whole string.
Thanks for the help!

a = line.split(/:/);
key = a.shift();
val = a.join(':');

Use the greedy operator (?) to only split the first instance.
line.split(/: (.+)?/, 2);

If you prefer an alternative to regexp consider this:
var split = line.split(':');
var key = split[0];
var val = split.slice(1).join(":");
Reference: split, slice, join.

Slightly more elegant:
a = line.match(/(.*?):(.*)/);
key = a[1];
val = a[2];

May be this approach will be the best for such purpose:
var a = line.match(/([^:\s]+)\s*:\s*(.*)/);
var key = a[1];
var val = a[2];
So, you can use tabulations in your config/data files of such structure and also not worry about spaces before or after your name-value delimiter ':'.
Or you can use primitive and fast string functions indexOf and substr to reach your goal in, I think, the fastest way (by CPU and RAM)
for ( ... line ... ) {
var delimPos = line.indexOf(':');
if (delimPos <= 0) {
continue; // Something wrong with this "line"
}
var key = line.substr(0, delimPos).trim();
var val = line.substr(delimPos + 1).trim();
// Do all you need with this key: val
}

Split string in two at first occurrence
To split a string with multiple i.e. columns : only at the first column occurrence
use Positive Lookbehind (?<=)
const a = "Description: this: is: nice";
const b = "Name: My Name";
console.log(a.split(/(?<=^[^:]*):/)); // ["Description", " this: is: nice"]
console.log(b.split(/(?<=^[^:]*):/)); // ["Name", " My Name"]
it basically consumes from Start of string ^ everything that is not a column [^:] zero or more times *. Once the positive lookbehind is done, finally matches the column :.
If you additionally want to remove one or more whitespaces following the column,
use /(?<=^[^:]*): */
Explanation on Regex101.com

function splitOnce(str, sep) {
const idx = str.indexOf(sep);
return [str.slice(0, idx), str.slice(idx+1)];
}
splitOnce("description: this string is not escaped: i hate these colons", ":")

How to extract a string using JavaScript Regex?

I'm trying to extract a substring from a file with JavaScript Regex. Here is a slice from the file :
DATE:20091201T220000
SUMMARY:Dad's birthday
the field I want to extract is "Summary". Here is the approach:
extractSummary : function(iCalContent) {
/*
input : iCal file content
return : Event summary
*/
var arr = iCalContent.match(/^SUMMARY\:(.)*$/g);
return(arr);
}

function extractSummary(iCalContent) {
var rx = /\nSUMMARY:(.*)\n/g;
var arr = rx.exec(iCalContent);
return arr[1];
}
You need these changes:
Put the * inside the parenthesis as
suggested above. Otherwise your matching
group will contain only one
character.
Get rid of the ^ and $. With the global option they match on start and end of the full string, rather than on start and end of lines. Match on explicit newlines instead.
I suppose you want the matching group (what's
inside the parenthesis) rather than
the full array? arr[0] is
the full match ("\nSUMMARY:...") and
the next indexes contain the group
matches.
String.match(regexp) is
supposed to return an array with the
matches. In my browser it doesn't (Safari on Mac returns only the full
match, not the groups), but
Regexp.exec(string) works.

You need to use the m flag:
multiline; treat beginning and end characters (^ and $) as working
over multiple lines (i.e., match the beginning or end of each line
(delimited by \n or \r), not only the very beginning or end of the
whole input string)
Also put the * in the right place:
"DATE:20091201T220000\r\nSUMMARY:Dad's birthday".match(/^SUMMARY\:(.*)$/gm);
//------------------------------------------------------------------^ ^
//-----------------------------------------------------------------------|

Your regular expression most likely wants to be
/\nSUMMARY:(.*)$/g
A helpful little trick I like to use is to default assign on match with an array.
var arr = iCalContent.match(/\nSUMMARY:(.*)$/g) || [""]; //could also use null for empty value
return arr[0];
This way you don't get annoying type errors when you go to use arr

This code works:
let str = "governance[string_i_want]";
let res = str.match(/[^governance\[](.*)[^\]]/g);
console.log(res);
res will equal "string_i_want". However, in this example res is still an array, so do not treat res like a string.
By grouping the characters I do not want, using [^string], and matching on what is between the brackets, the code extracts the string I want!
You can try it out here: https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_match_regexp
Good luck.

(.*) instead of (.)* would be a start. The latter will only capture the last character on the line.
Also, no need to escape the :.

You should use this :
var arr = iCalContent.match(/^SUMMARY\:(.)*$/g);
return(arr[0]);

this is how you can parse iCal files with javascript
function calParse(str) {
function parse() {
var obj = {};
while(str.length) {
var p = str.shift().split(":");
var k = p.shift(), p = p.join();
switch(k) {
case "BEGIN":
obj[p] = parse();
break;
case "END":
return obj;
default:
obj[k] = p;
}
}
return obj;
}
str = str.replace(/\n /g, " ").split("\n");
return parse().VCALENDAR;
}
example =
'BEGIN:VCALENDAR\n'+
'VERSION:2.0\n'+
'PRODID:-//hacksw/handcal//NONSGML v1.0//EN\n'+
'BEGIN:VEVENT\n'+
'DTSTART:19970714T170000Z\n'+
'DTEND:19970715T035959Z\n'+
'SUMMARY:Bastille Day Party\n'+
'END:VEVENT\n'+
'END:VCALENDAR\n'
cal = calParse(example);
alert(cal.VEVENT.SUMMARY);