Develop Reference

Regular Expression to get the last word from TitleCase, camelCase

I'm trying to split a TitleCase (or camelCase) string into precisely two parts using javascript. I know I can split it into multiple parts by using the lookahead:
"StringToSplit".split(/(?=[A-Z])/);
And it will make an array ['String', 'To', 'Split']
But what I need is to break it into precisely TWO parts, to produce an array like this:
['StringTo', 'Split']
Where the second element is always the last word in the TitleCase, and the first element is everything else that precedes it.

Is this what you are looking for ?
"StringToSplit".split(/(?=[A-Z][a-z]+$)/); // ["StringTo", "Split"]
Improved based on lolol answer :
"StringToSplit".split(/(?=[A-Z][^A-Z]+$)/); // ["StringTo", "Split"]

Use it like this:
s = "StringToSplit";
last = s.replace(/^.*?([A-Z][a-z]+)(?=$)/, '$1'); // Split
first = s.replace(last, ''); // StringTo
tok = [first, last]; // ["StringTo", "Split"]

You could use
(function(){
return [this.slice(0,this.length-1).join(''), this[this.length-1]];
}).call("StringToSplit".split(/(?=[A-Z])/));
//=> ["StringTo", "Split"]
In [other] words:
create the Array using split from a String
join a slice of that Array without the last element of that
Array
add that and the last element to a final Array

Replace .split() with .match() using regex in javascript

I'm having difficulties with constructing some regular expressions using Javascript.
What I need:
I have a string like: Woman|{Man|Boy} or {Girl|Woman}|Man or Woman|Man etc.
I need to split this string by '|' separator, but I don't want it to be split inside curly brackets.
Examples of strings and desired results:
// Expample 1
string: 'Woman|{Man|Boy}'
result: [0] = 'Woman', [1] = '{Man|Boy}'
// Example 2
string '{Woman|Girl}|{Man|Boy}'
result: [0] = '{Woman|Girl}', [1] = '{Man|Boy}'
I can't change "|" symbol to another inside the brackets because the given strings are the result of a recursive function. For example, the original string could be
'Nature|Computers|{{Girls|Women}|{Boys|Men}}'

try this:
var reg=/\|(?![^{}]+})/g;
Example results:
var a = 'Woman|{Man|Boy}';
var b = '{Woman|Girl}|{Man|Boy}';
a.split(reg)
["Woman", "{Man|Boy}"]
b.split(reg)
["{Woman|Girl}", "{Man|Boy}"]
for your another question:
"Now I have another, but a bit similar problem. I need to parse all containers from the string. Syntax of the each container is {sometrash}. The problem is that container can contain another containers, but I need to parse only "the most relative" container. mystring.match(/\{+.+?\}+/gi); which I use doesn't work correctly. Could you correct this regex, please? "
you can use this regex:
var reg=/\{[^{}]+\}/g;
Example results:
var a = 'Nature|Computers|{{Girls|Women}|{Boys|Men}}';
a.match(reg)
["{Girls|Women}", "{Boys|Men}"]

You can use
.match(/[^|]+|\{[^}]*\}/g)
to match those. However, if you have a nesting of arbitrary depth then you'll need to use a parser, [javascript] regex won't be capable of doing that.

Test this:
([a-zA-Z0-9]*\|[a-zA-Z0-9]*)|{[a-zA-Z0-9]*\|[a-zA-Z0-9]*}

What does split function look like?

I came across this statement :
userName = document.cookie.split("=")[1];
after reading about split statement here at w3schools. which says that syntax of split is
string.split(separator, limit). Then what does the square bracket after first parens. mean ?
If this is true what does split function look like ?

String.split(separator, limit) returns an array. In Javascript, you can access array values by index using the square brackets. Arrays are zero-based, 0 is the first element, 1 the second and so on.
The equivalent of your code would be:
var arr = document.cookie.split("=");
userName = arr[1];
This separates the document.cookie by the equal-sign (=) and takes the second element (index 1) from it. document.cookie is a special property (datatype: String) of the document object which contains all cookies of a webpage, separated by the ; character. E.g. if document.cookie contains name=Adam, the array arr will contain the values name and Adam. The second one is stored in userName.
Note that if the cookie contains multiple values, or if the value contains multiple equal-signs, it won't work. Consider the next cases:
document.cookie contains name=Adam; home=Nowhere. Using the above code, this would make userName contain Adam; home because the string is separated by the equal-sign, and then the second value is taken.
document.cookie contains home=Nowhere; name=Adam. This would result in userName containing Nowhere; name
document.cookie contains name=Adam=cool. In this case, userName would be Adam and not Adam=cool.
Also, w3schools is not that reliable. Use more authorative sources like the Mozilla Developer Network:
document.cookie
String.split
Array

The split function returns an array of strings split by the given separator. With the square bracket you are accessing the nth element of that (returned) array.
If you are familiar with Java, its the same behavior as the String.split() method there.

It gets the second index of the resulting array
Same as:
var split = document.cookie.split("=");
var userName = split[1];

split returns an array of strings. So square brackets mean get second string from the returned array.

The square bracket in the code you supplied is accessing the second element of the array returned by split(). The function itself returns an array. That code would be the same as:
var temp = document.cookie.split("=");
userName = temp[1];

Split would return an array e.g. [1, 2, 3]. If you supply the square bracket after it, it will return the specified key in the brackets, in this case userName would be 2

You shouldn't be using w3schools, but...
In JavaScript, function parameters are optional and it is possible to supply fewer parameters than the function expects. The extra parameters in the function are then undefined. Some functions are programmed to deal with that possibility and string.split is one of them.
The other part has to do with the fact that split returns an array. Arrays can then be indexed using the square bracket notation, hence the [1] after the function call.

Regex to extract substring, returning 2 results for some reason

I need to do a lot of regex things in javascript but am having some issues with the syntax and I can't seem to find a definitive resource on this.. for some reason when I do:
var tesst = "afskfsd33j"
var test = tesst.match(/a(.*)j/);
alert (test)
it shows
"afskfsd33j, fskfsd33"
I'm not sure why its giving this output of original and the matched string, I am wondering how I can get it to just give the match (essentially extracting the part I want from the original string)
Thanks for any advice

match returns an array.
The default string representation of an array in JavaScript is the elements of the array separated by commas. In this case the desired result is in the second element of the array:
var tesst = "afskfsd33j"
var test = tesst.match(/a(.*)j/);
alert (test[1]);

Each group defined by parenthesis () is captured during processing and each captured group content is pushed into result array in same order as groups within pattern starts. See more on http://www.regular-expressions.info/brackets.html and http://www.regular-expressions.info/refcapture.html (choose right language to see supported features)
var source = "afskfsd33j"
var result = source.match(/a(.*)j/);
result: ["afskfsd33j", "fskfsd33"]
The reason why you received this exact result is following:
First value in array is the first found string which confirms the entire pattern. So it should definitely start with "a" followed by any number of any characters and ends with first "j" char after starting "a".
Second value in array is captured group defined by parenthesis. In your case group contain entire pattern match without content defined outside parenthesis, so exactly "fskfsd33".
If you want to get rid of second value in array you may define pattern like this:
/a(?:.*)j/
where "?:" means that group of chars which match the content in parenthesis will not be part of resulting array.
Other options might be in this simple case to write pattern without any group because it is not necessary to use group at all:
/a.*j/
If you want to just check whether source text matches the pattern and does not care about which text it found than you may try:
var result = /a.*j/.test(source);
The result should return then only true|false values. For more info see http://www.javascriptkit.com/javatutors/re3.shtml

I think your problem is that the match method is returning an array. The 0th item in the array is the original string, the 1st thru nth items correspond to the 1st through nth matched parenthesised items. Your "alert()" call is showing the entire array.

Just get rid of the parenthesis and that will give you an array with one element and:
Change this line
var test = tesst.match(/a(.*)j/);
To this
var test = tesst.match(/a.*j/);
If you add parenthesis the match() function will find two match for you one for whole expression and one for the expression inside the parenthesis
Also according to developer.mozilla.org docs :
If you only want the first match found, you might want to use
RegExp.exec() instead.
You can use the below code:
RegExp(/a.*j/).exec("afskfsd33j")

I've just had the same problem.
You only get the text twice in your result if you include a match group (in brackets) and the 'g' (global) modifier.
The first item always is the first result, normally OK when using match(reg) on a short string, however when using a construct like:
while ((result = reg.exec(string)) !== null){
console.log(result);
}
the results are a little different.
Try the following code:
var regEx = new RegExp('([0-9]+ (cat|fish))','g'), sampleString="1 cat and 2 fish";
var result = sample_string.match(regEx);
console.log(JSON.stringify(result));
// ["1 cat","2 fish"]
var reg = new RegExp('[0-9]+ (cat|fish)','g'), sampleString="1 cat and 2 fish";
while ((result = reg.exec(sampleString)) !== null) {
console.dir(JSON.stringify(result))
};
// '["1 cat","cat"]'
// '["2 fish","fish"]'
var reg = new RegExp('([0-9]+ (cat|fish))','g'), sampleString="1 cat and 2 fish";
while ((result = reg.exec(sampleString)) !== null){
console.dir(JSON.stringify(result))
};
// '["1 cat","1 cat","cat"]'
// '["2 fish","2 fish","fish"]'
(tested on recent V8 - Chrome, Node.js)
The best answer is currently a comment which I can't upvote, so credit to #Mic.

assign matched values from jquery regex match to string variable

I am doing it wrong. I know.
I want to assign the matched text that is the result of a regex to a string var.
basically the regex is supposed to pull out anything in between two colons
so blah:xx:blahdeeblah
would result in xx
var matchedString= $(current).match('[^.:]+):(.*?):([^.:]+');
alert(matchedString);
I am looking to get this to put the xx in my matchedString variable.
I checked the jquery docs and they say that match should return an array. (string char array?)
When I run this nothing happens, No errors in the console but I tested the regex and it works outside of js. I am starting to think I am just doing the regex wrong or I am completely not getting how the match function works altogether

I checked the jquery docs and they say that match should return an array.
No such method exists for jQuery. match is a standard javascript method of a string. So using your example, this might be
var str = "blah:xx:blahdeeblah";
var matchedString = str.match(/([^.:]+):(.*?):([^.:]+)/);
alert(matchedString[2]);
// -> "xx"
However, you really don't need a regular expression for this. You can use another string method, split() to divide the string into an array of strings using a separator:
var str = "blah:xx:blahdeeblah";
var matchedString = str.split(":"); // split on the : character
alert(matchedString[1]);
// -> "xx"
String.match
String.split