Regex - Javascript capture area

Question

I want to capture only a area of the Match part. I have following String: " type1-class1 type1-class2 type2-class4 type2-type1-class3 " and i want following result ["class1", "class2"]. I am searching the class by the type. I have tried following:

console.log(" type1-class1 type1-class2 type2-class4 type2-type1-class3 ".match(/\btype1-.*?(?= )/g))
// Result: ["type1-class1", "type1-class2", "type1-class3"]

Furthermore i have tried following:

console.log(" type1-class1 type1-class2 type2-class4 type2-type1-class3 ".match(/(?= type1-).*?(?= )/g));
// Result: ["", ""]

How can i disable the capture on the beginning of a Regex?

What do you mean by disable the capture on the beginning of a Regex? — evolutionxbox
– evolutionxbox, Commented Sep 5, 2016 at 10:51
Do you have to use String#match rather than an exec loop? — T.J. Crowder
– T.J. Crowder, Commented Sep 5, 2016 at 10:52
Because i can use (?= ...) to match but not capture, this is only working on the center/end of a match but not at the beginning. However, i want to match a string and only to get a part of it. As i mentioned above i want to match " type1-class1 " and get "class1" and the same on " type1-class2 " and get "class2". — Kevin B.
– Kevin B., Commented Sep 5, 2016 at 10:55
match doesn't work the way you want it to with /g and multiple matches, You will have to use stackoverflow.com/a/10939979/3355076 — Christopher Reid
– Christopher Reid, Commented Sep 5, 2016 at 10:56

Kevin B. · Accepted Answer · 2016-09-05 11:54:12Z

4

I'd use an exec loop. The regular expression is /(?:^|\s)type1-([^ ]+)/g, e.g., "Following a type-1 that's at the beginning of the string or just after whitespace, capture everything until the next whitespace or end of string. (With your string as given, we don't need the alternation with ^, but I wanted to allow for "type1-class1" at beginning of string.) We then collect the captures in a loop:

var rex = /(?:^|\s)type1-([^ ]+)/g;
var str = " type1-class1 type1-class2 type2-class4 type2-type1-class3 ";
var classes = [];
var m;
while ((m = rex.exec(str)) != null) {
  classes.push(m[1]);
}
console.log(classes);

edited Sep 5, 2016 at 11:54

Kevin B.

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answered Sep 5, 2016 at 10:57

T.J. Crowder

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Comments

Karpak · Accepted Answer · 2016-09-05 11:09:51Z

0

is this what you are expecting?

console.log(" type1-class1 type1-class2 type2-class4 type2-type1-class3 ".match(/ type1-.*?(?= )/g).map(x=>x.replace(/type1-/g,"").trim()))

edited Sep 5, 2016 at 11:09

answered Sep 5, 2016 at 11:04

Karpak

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4 Comments

T.J. Crowder Over a year ago

Answers shouldn't be questions. Also, say what you changed, and why.

T.J. Crowder Over a year ago

"is this what you are expecting?" Clearly not, as the OP clearly says he/she wants ["class1", "class2"] but the above returns ["class1", "class2", "class3"]

T.J. Crowder Over a year ago

But the idea of post-processing with map isn't a bad one, might be worth fleshing it out to make this a useful answer.

Karpak Over a year ago

Thanks T.JCrowder for your comments. Edited this answer itself. I hope this answers AntiMuffin's query.

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