I have a string that can be a comma separated list of \w, such as:
abc123
abc123,def456,ghi789
I am trying to find a JavaScript regexp that will return ['abc123'] (first case) or ['abc123', 'def456', 'ghi789'] (without the comma).
I tried:
^(\w+,?)+$ -- Nope, as only the last repeating pattern will be matched, 789
^(?:(\w+),?)+$ -- Same story. I am using non-capturing bracket. However, the capturing just doesn't seem to happen for the repeated word
Is what I am trying to do even possible with regexp? I tried pretty much every combination of grouping, using capturing and non-capturing brackets, and still not managed to get this happening...
If you want to discard the whole input when there is something wrong, the simplest way is to validate, then split:
if (/^\w+(,\w+)*$/.test(input)) {
var values = input.split(',');
// Process the values here
}
If you want to allow empty value, change \w+ to \w*.
Trying to match and validate at the same time with single regex requires emulation of \G feature, which assert the position of the last match. Why is \G required? Since it prevents the engine from retrying the match at the next position and bypass your validation. Remember than ECMA Script regex doesn't have look-behind, so you can't differentiate between the position of an invalid character and the character(s) after it:
something,=bad,orisit,cor&rupt
^^ ^^
When you can't differentiate between the 2 positions, you can't rely on the engine to do a match-all operation alone. While it is possible to use a while loop with RegExp.exec and assert the position of last match yourself, why would you do so when there is a cleaner option?
If you want to savage whatever available, torazaburo's answer is a viable option.
Live demo
Try this regex :
'/([^,]+)/'
Alternatively, strings in javascript have a split method that can split a string based on a delimeter:
s.split(',')
Split on the comma first, then filter out results that do not match:
str.split(',').filter(function(s) { return /^\w+$/.test(s); })
This regex pattern separates numerical value in new line which contains special character such as .,,,# and so on.
var val = [1234,1213.1212, 1.3, 1.4]
var re = /[0-9]*[0-9]/gi;
var str = "abc123,def456, asda12, 1a2ass, yy8,ghi789";
var re = /[a-z]{3}\d{3}/g;
var list = str.match(re);
document.write("<BR> list.length: " + list.length);
for(var i=0; i < list.length; i++) {
document.write("<BR>list(" + i + "): " + list[i]);
}
This will get only "abc123" code style in the list and nothing else.
May be you can use split function
var st = "abc123,def456,ghi789";
var res = st.split(',');
Related
I'm trying to write a regex that will return true if it matches the format below, otherwise, it should return false. It should only allow words as below:
Positive match (return true)
UA-1234-1,UA-12345-2,UA-34578-2
Negative match (return false or null)
Note: A is missing after U
UA-1234-1,U-12345-2
It should always give me true when the string passed to regex is
UA-1234-1,UA-12345-2,UA-34578-2,...........
Below is what I am trying to do but it is matching only the first element and not returning null.
var pattern=/^UA-[0-9]+(-[0-9]+)?/g;
pattern.match("UA-1234-1,UA-12345-2,UA-34578-2");
pattern.exec("UA-1234-1,UA-12345-2,UA-34578-2)
Thanks in advance. Help is greatly appreciated.
The pattern you need is a pattern enclosed with anchors (^ - start of string and $ - end of string) that matches your pattern at first (the initial "block") and then matches 0 or more occurrences of a , followed with the block pattern.
It looks like /^BLOCK(?:,BLOCK)*$/. You may introduce optional whitespaces in between, e.g. /^BLOCK(?:,\s*BLOCK)*$/.
In the end, the pattern looks like ^UA-[0-9]+(?:-[0-9]+)?(?:,UA-[0-9]+(?:-[0-9]+)?)*$. It is best to build it dynamically to keep it readable and easy to maintain:
const block = "UA-[0-9]+(?:-[0-9]+)?";
let rx = new RegExp(`^${block}(?:,${block})*$`); // RegExp("^" + block + "(?:," + block + ")*$") // for non-ES6
let tests = ['UA-1234-1,UA-12345-2,UA-34578-2', 'UA-1234-1,U-12345-2'];
for (var s of tests) {
console.log(s, "=>", rx.test(s));
}
split the string by commas, and test each element instead.
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));
What I Tried
var test = "asdfdas ABCD EFGH";
var regex = /^\S+( [A-Z]{4})+$/;
// Also tried: /^\S+( [A-Z]{4})+$/g
// And: /^\S+( [A-Z]{4})+?$/g
var matches = test.match(regex);
I made a JSFiddle.
What I Expect
The variable matches should become this array:
[
"asdfdas ABCD EFGH",
" ABCD",
" EFGH"
]
What I Get
The variable matches is actually this array:
[
"asdfdas ABCD EFGH",
" EFGH"
]
My Thoughts
My guess is that there's something I'm missing with the capture group and/or $ logic. Any help would be appreciated. (I know I can figure out how to do this in multiple regular expressions, but I want to understand what is happening here.)
Yes, that’s exactly what it does; you’re not doing anything wrong. When a group is given a quantifier, it only captures its last match, and that’s all it will ever do in JavaScript. The general fix is to use multiple regular expressions, as you said, e.g.
var test = "asdfdas ABCD EFGH";
var match = test.match(/^\S+((?: [A-Z]{4})+)$/); // capture all repetitions
var matches = match[1].match(/ [A-Z]{4}/g); // match again to get individual ones
I am trying to get a serial number from a zigbee packet (i.e get from 702442500 *13*32*702442500#9).
So far, I've tried this:
test = "*#*0##*13*32*702442500#9##";
test.match("\*#\*0##\*13\*32\*(.*)#9##");
And this:
test.match("*#*0##*13*32*(.*)#9##");
With no luck. How do I get a valid regular expression that does what I want?
The below regex matches the number which has atleast three digits,
/([0-9][0-9][0-9]+)/
DEMO
If you want to extract the big number, you can use:
/\*#\*0##\*13\*32\*([^#]+)#9##/
Note that I use delimiters / that are needed to write a pattern in Javascript (without the regexp object syntax). When you use this syntax, (double)? quotes are not needed. I use [^#]+ instead of .* because it is more clear and more efficent for the regex engine.
The easiest way to grab that portion of the string would be to use
var regex = /(\*\d{3,}#)/g,
test = "*13*32*702442500#9";
var match = test.match(regex).slice(1,-1);
This captures a * followed by 3 or more \d (numbers) until it reaches an octothorpe. Using the global (/g) modifier will cause it to return an array of matches.
For example, if
var test = "*13*32*702442500#9
*#*0##*13*32*702442500#9##";
then, test.match(regex) will return ["*702442500#", "*702442500#"]. You can then slice the elements of this array:
var results = [],
test = "... above ... ",
regex = /(\*\d{3,}#)/g,
matches = test.match(regex);
matches.forEach(function (d) {
results.push(d.slice(1,-1));
})
// results : `["702442500", "702442500"]`
have a regex problem :(
what i would like to do is to find out the contents between two or more numbers.
var string = "90+*-+80-+/*70"
im trying to edit the symbols in between so it only shows up the last symbol and not the ones before it. so trying to get the above variable to be turned into 90+80*70. although this is just an example i have no idea how to do this. the length of the numbers, how many "sets" of numbers and the length of the symbols in between could be anything.
many thanks,
Steve,
The trick is in matching '90+-+' and '80-+/' seperately, and selecting only the number and the last constant.
The expression for finding the a number followed by 1 or more non-numbers would be
\d+[^\d]+
To select the number and the last non-number, add parens:
(\d+)[^\d]*([^\d])
Finally add a /g to repeat the procedure for each match, and replace it with the 2 matched groups for each match:
js> '90+*-+80-+/*70'.replace(/(\d+)[^\d]*([^\d])/g, '$1$2');
90+80*70
js>
Or you can use lookahead assertion and simply remove all non-numerical characters which are not last: "90+*-+80-+/*70".replace(/[^0-9]+(?=[^0-9])/g,'');
You can use a regular expression to match the non-digits and a callback function to process the match and decide what to replace:
var test = "90+*-+80-+/*70";
var out = test.replace(/[^\d]+/g, function(str) {
return(str.substr(-1));
})
alert(out);
See it work here: http://jsfiddle.net/jfriend00/Tncya/
This works by using a regular expression to match sequences of non-digits and then replacing that sequence of non-digits with the last character in the matched sequence.
i would use this tutorial, first, then review this for javascript-specific regex questions.
This should do it -
var string = "90+*-+80-+/*70"
var result = '';
var arr = string.split(/(\d+)/)
for (i = 0; i < arr.length; i++) {
if (!isNaN(arr[i])) result = result + arr[i];
else result = result + arr[i].slice(arr[i].length - 1, arr[i].length);
}
alert(result);
Working demo - http://jsfiddle.net/ipr101/SA2pR/
Similar to #Arnout Engelen
var string = "90+*-+80-+/*70";
string = string.replace(/(\d+)[^\d]*([^\d])(?=\d+)/g, '$1$2');
This was my first thinking of how the RegEx should perform, it also looks ahead to make sure the non-digit pattern is followed by another digit, which is what the question asked for (between two numbers)
Similar to #jfriend00
var string = "90+*-+80-+/*70";
string = string.replace( /(\d+?)([^\d]+?)(?=\d+)/g
, function(){
return arguments[1] + arguments[2].substr(-1);
});
Instead of only matching on non-digits, it matches on non-digits between two numbers, which is what the question asked
Why would this be any better?
If your equation was embedded in a paragraph or string of text. Like:
This is a test where I want to clean up something like 90+*-+80-+/*70 and don't want to scrap the whole paragraph.
Result (Expected) :
This is a test where I want to clean up something like 90+80*70 and don't want to scrap the whole paragraph.
Why would this not be any better?
There is more pattern matching, which makes it theoretically slower (negligible)
It would fail if your paragraph had embedded numbers. Like:
This is a paragraph where Sally bought 4 eggs from the supermarket, but only 3 of them made it back in one piece.
Result (Unexpected):
This is a paragraph where Sally bought 4 3 of them made it back in one piece.