Develop Reference

How to split a string by a character not directly preceded by a character of the same type?

Let's say I have a string: "We.need..to...split.asap". What I would like to do is to split the string by the delimiter ., but I only wish to split by the first . and include any recurring .s in the succeeding token.
Expected output:
["We", "need", ".to", "..split", "asap"]
In other languages, I know that this is possible with a look-behind /(?<!\.)\./ but Javascript unfortunately does not support such a feature.
I am curious to see your answers to this question. Perhaps there is a clever use of look-aheads that presently evades me?
I was considering reversing the string, then re-reversing the tokens, but that seems like too much work for what I am after... plus controversy: How do you reverse a string in place in JavaScript?
Thanks for the help!

Here's a variation of the answer by guest271314 that handles more than two consecutive delimiters:
var text = "We.need.to...split.asap";
var re = /(\.*[^.]+)\./;
var items = text.split(re).filter(function(val) { return val.length > 0; });
It uses the detail that if the split expression includes a capture group, the captured items are included in the returned array. These capture groups are actually the only thing we are interested in; the tokens are all empty strings, which we filter out.
EDIT: Unfortunately there's perhaps one slight bug with this. If the text to be split starts with a delimiter, that will be included in the first token. If that's an issue, it can be remedied with:
var re = /(?:^|(\.*[^.]+))\./;
var items = text.split(re).filter(function(val) { return !!val; });
(I think this regex is ugly and would welcome an improvement.)

You can do this without any lookaheads:
var subject = "We.need.to....split.asap";
var regex = /\.?(\.*[^.]+)/g;
var matches, output = [];
while(matches = regex.exec(subject)) {
output.push(matches[1]);
}
document.write(JSON.stringify(output));
It seemed like it'd work in one line, as it did on https://regex101.com/r/cO1dP3/1, but had to be expanded in the code above because the /g option by default prevents capturing groups from returning with .match (i.e. the correct data was in the capturing groups, but we couldn't immediately access them without doing the above).
See: JavaScript Regex Global Match Groups
An alternative solution with the original one liner (plus one line) is:
document.write(JSON.stringify(
"We.need.to....split.asap".match(/\.?(\.*[^.]+)/g)
.map(function(s) { return s.replace(/^\./, ''); })
));
Take your pick!

Note: This answer can't handle more than 2 consecutive delimiters, since it was written according to the example in the revision 1 of the question, which was not very clear about such cases.
var text = "We.need.to..split.asap";
// split "." if followed by "."
var res = text.split(/\.(?=\.)/).map(function(val, key) {
// if `val[0]` does not begin with "." split "."
// else split "." if not followed by "."
return val[0] !== "." ? val.split(/\./) : val.split(/\.(?!.*\.)/)
});
// concat arrays `res[0]` , `res[1]`
res = res[0].concat(res[1]);
document.write(JSON.stringify(res));

extracting middle OR final part of a string

I want to extract only the first fontname out of a URL-string from the Google Webfont Directory. Here are some examples of possible strings and what part should be returned:
fonts.googleapis.com/css?family=Raleway // "Raleway"
fonts.googleapis.com/css?family=Caesar+Dressing // "Caesar Dressing"
fonts.googleapis.com/css?family=Raleway:300,400 // "Raleway"
fonts.googleapis.com/css?family=Raleway|Fondamento // "Raleway"
fonts.googleapis.com/css?family=Caesar+Dressing|Raleway:300,400|Fondamento // "Caesar Dressing"
So sometimes it's just one fontname, sometimes it has a weight indicated by a colon (:) and sometimes there are more fontnames divided by a pipe (|).
I have tried /family=(\S*)[:|]/ but it only matches the strings with :or |. I could do it like this, but it's not a nice solution:
var fontUrl = "fonts.googleapis.com/css?family=Caesar+Dressing|Raleway:300,400|Fondamento";
var fontName = /family=(\S*)/.exec(fontUrl)[1].replace(/\+/, " ");
if (fontName.indexOf(':') != -1){
fontName = fontName.split(':')[0];
}
if (fontName.indexOf('|') != -1){
fontName = fontName.split('|')[0];
}
console.log(fontName);
Is there a nice regex solution to this?

Instead of matching the character that (might) follow the string you want, match only the string you want except those characters:
/family=([^\s:|]*)/
Alternatively, you'd use a lookahead like this:
/family=(\S*?)(?=$|[:|])/

That should be better:
/family=([^:|]*)/
Of course for the + case, you'll have to replace it afterwards (or before maybe).

You can use (choose the i and m modifier in all case):
family=([a-z]+\+?[a-z]+)
or more simply
family=([a-z+]+)
or to avoid matching the + char:
family=([a-z]+)\+?([a-z]+)?
but it is an easyer way to use the second solution, and to replace the + chars with a space after.

try this:
/family\=(\S+?)[\:\|,]{0,2}\S*/ims

No regex is required in this case, unless you are good with regex's or test them thoroughly then you are likely to make mistakes.
var fontUrls = [];
fontUrls.push("fonts.googleapis.com/css?family=Raleway");
fontUrls.push("fonts.googleapis.com/css?family=Caesar+Dressing");
fontUrls.push("fonts.googleapis.com/css?family=Raleway:300,400");
fontUrls.push("fonts.googleapis.com/css?family=Raleway|Fondamento");
fontUrls.push("fonts.googleapis.com/css?family=Caesar+Dressing|Raleway:300,400|Fondamento");
function getFirstFont(url) {
return url.split("=")[1].split("|")[0].split(":")[0];
}
fontUrls.forEach(function (fontUrl) {
console.log(getFirstFont(fontUrl));
});
on jsfiddle

Javascript regex match for string "game_1"

I just can't get this thing to work in javascript. So, I have a text "game_1" without the quotes and now i want to get that number out of it and I tried this:
var idText = "game_1";
re = /game_(.*?)/;
found = idText.match(re);
var ajdi = found[1];
alert( ajdi );
But it doesn't work - please point out where am I going wrong.

If you're only matching a number, you may want to try
/game_([0-9]+)/
as your regular expression. That will match at least one number, which seems to be what you need. You entered a regexp that allows for 0 characters (*) and let it select the shortest possible result (?), which may be a problem (and match you 0 characters), depending on the regex engine.

If this is the complete text, then there is no need for regular expressions:
var id = +str.split('_')[1];
or
var id = +str.replace('game_', '');
(unary + is to convert the string to a number)
If you insist on regular expression, you have to anchor the expression:
/^game_(.*?)$/
or make the * greedy by omitting the ?:
/game_(.*)/
Better is to make the expression more restrictive as #Naltharial suggested.

Simple string manipulation:
var idText = "game_1",
adji = parseInt(idText.substring(5), 10);

* means zero or more occurrences. It seems that combining it with a greediness controller ? results in zero match.
You could replace * with + (which means one or more occurrences), but as #Felix Kling notes, it would only match one digit.
Better to ditch the ? completely.
http://jsfiddle.net/G8Qt7/2/

Try "game_1".replace(/^(game_)/, '')
this will return the number

You can simply use this re /\d+/ to get any number inside your string

Strip all non-numeric characters from string in JavaScript

Consider a non-DOM scenario where you'd want to remove all non-numeric characters from a string using JavaScript/ECMAScript. Any characters that are in range 0 - 9 should be kept.
var myString = 'abc123.8<blah>';
//desired output is 1238
How would you achieve this in plain JavaScript? Please remember this is a non-DOM scenario, so jQuery and other solutions involving browser and keypress events aren't suitable.

Use the string's .replace method with a regex of \D, which is a shorthand character class that matches all non-digits:
myString = myString.replace(/\D/g,'');

If you need this to leave the dot for float numbers, use this
var s = "-12345.50 €".replace(/[^\d.-]/g, ''); // gives "-12345.50"

Use a regular expression, if your script implementation supports them. Something like:
myString.replace(/[^0-9]/g, '');

You can use a RegExp to replace all the non-digit characters:
var myString = 'abc123.8<blah>';
myString = myString.replace(/[^\d]/g, ''); // 1238

Something along the lines of:
yourString = yourString.replace ( /[^0-9]/g, '' );

Short function to remove all non-numeric characters but keep the decimal (and return the number):
parseNum = str => +str.replace(/[^.\d]/g, '');
let str = 'a1b2c.d3e';
console.log(parseNum(str));

In Angular / Ionic / VueJS -- I just came up with a simple method of:
stripNaN(txt: any) {
return txt.toString().replace(/[^a-zA-Z0-9]/g, "");
}
Usage on the view:
<a [href]="'tel:'+stripNaN(single.meta['phone'])" [innerHTML]="stripNaN(single.meta['phone'])"></a>

The problem with these answers above, is that it assumes whole numbers. But if you need a floating point value, then the previous reg string will remove the decimal point.
To correct this you need write a negated character class with ^
var mystring = mystring.replace(/[^0-9.]/g, '');

try
myString.match(/\d/g).join``
var myString = 'abc123.8<blah>'
console.log( myString.match(/\d/g).join`` );

Unfortunately none of the answers above worked for me.
I was looking to convert currency numbers from strings like $123,232,122.11 (1232332122.11) or USD 123,122.892 (123122.892) or any currency like ₹ 98,79,112.50 (9879112.5) to give me a number output including the decimal pointer.
Had to make my own regex which looks something like this:
str = str.match(/\d|\./g).join('');

This,
.match(/\d|\.|\-/g).join('');
Handles both , and . also -
Example:
"Balance -$100,00.50".match(/\d|\.|\-/g).join('');
Outputs
10000.50

we are in 2017 now you can also use ES2016
var a = 'abc123.8<blah>';
console.log([...a].filter( e => isFinite(e)).join(''));
or
console.log([...'abc123.8<blah>'].filter( e => isFinite(e)).join(''));
The result is
1238

JavaScript match substring after RegExp

I have a string that look something like
something30-mr200
I would like to get everything after the mr (basically the # followed by mr) *always there is going to be the -mr
Any help will be appreciate it.

You can use a regexp like the one Bart gave you, but I suggest using match rather than replace, since in case a match is not found, the result is the entire string when using replace, while null when using match, which seems more logical. (as a general though).
Something like this would do the trick:
function getNumber(string) {
var matches = string.match(/-mr([0-9]+)/);
return matches[1];
}
console.log(getNumber("something30-mr200"));

var result = "something30-mr200".split("mr")[1];
or
var result = "something30-mr200".match(/mr(.*)/)[1];

Why not simply:
-mr(\d+)
Then getting the contents of the capture group?

What about:
function getNumber(input) { // rename with a meaningful name
var match = input.match(/^.*-mr(\d+)$/);
if (match) { // check if the input string matched the pattern
return match[1]; // get the capturing group
}
}
getNumber("something30-mr200"); // "200"

This may work for you:
// Perform the reg exp test
new RegExp(".*-mr(\d+)").test("something30-mr200");
// result will equal the value of the first subexpression
var result = RegExp.$1;

What about finding the position of -mr, then get the substring from there + 3?
It's not regex, but seems to work given your description?