Javascript & regular expression

Question

I have this string

java=10514;js=237;jsp=3995;web=5;xml=42

and I'd like to extract, in separate variables, the value numbers for each language, using javascript and a regular expression that is, for the "java" case, the follow

(?<=java=).*?(?=;|$)

I've tried this code

var myString = "java=10514;js=237;jsp=3995;web=5;xml=42";
var regexp_java = new RegExp('(?<=java=).*?(?=;|$)', 'g');    
var ncloc_java = sonar_myString.match(regexp_java);
var regexp_js = new RegExp('(?<=js=).*?(?=;|$)', 'g');    
var ncloc_js = sonar_myString.match(regexp_js);
var regexp_jsp = new RegExp('(?<=jsp=).*?(?=;|$)', 'g');    
var ncloc_jsp = sonar_myString.match(regexp_jsp);
var regexp_web = new RegExp('(?<=web=).*?(?=;|$)', 'g');    
var ncloc_web = sonar_myString.match(regexp_web);
var regexp_jsp = new RegExp('(?<=jsp=).*?(?=;|$)', 'g');    
var ncloc_jsp = sonar_myString.match(regexp_jsp);

but it doesn't work.

Any suggestion will be appreciated and thank you in advance

Any reason it has to be regex, rather than simple string manipulation? — VLAZ
– VLAZ, Commented Dec 27, 2022 at 8:43

Tim Biegeleisen · Accepted Answer · 2022-12-27 08:46:27Z

3

I believe that you are using the wrong data structure here. Rather than trying to use individual variables for each language, you can instead use a hashmap. First split to the string on semicolon, and then stream that to get each language and value.

var input = "java=10514;js=237;jsp=3995;web=5;xml=42";
var map = {};
input.split(";").forEach(x => map[x.split("=")[0]] = x.split("=")[1]);
console.log(map);

answered Dec 27, 2022 at 8:46

Tim Biegeleisen

526k32 gold badges323 silver badges399 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

The fourth bird Over a year ago

Hi there, all is well? Do you agree with the duplicate here?

Tim Biegeleisen Over a year ago

@Thefourthbird As a matter of fact, no, I don't. That duplicate doesn't really cover this question.

Juljo Shahini · Accepted Answer · 2022-12-27 08:56:26Z

2

Does it really need to be done with Regex? Anyways I'm providing you with 2 solutions.

const string = "java=10514;js=237;jsp=3995;web=5;xml=42";

let result1 = string.split(';').reduce((acc, curr) => {
  let [key, value] = curr.split('=');
  acc[key] = value;
  return acc;
}, {});

console.log(result1);

let result2 = {};
let regex = /([a-z]+)\s*=\s*(\d+)/g;
let check;

while (check= regex.exec(string)) {
  result2[check[1]] = check[2];
}

console.log(result2);

answered Dec 27, 2022 at 8:56

Juljo Shahini

14810 bronze badges

Comments

The fourth bird · Accepted Answer · 2022-12-27 09:27:30Z

2

You don't have to create separate patterns and variables, Instead you can use 2 capture groups and then create an object with keys and values (assuming there are no duplicate keys)

\b(java|jsp?|web|xml)=([^;\s]+)

Explanation

\b A word boundary
(java|jsp?|web|xml) Match one of the alternatives
= Match literally
([^;\s]+) Capture group 2, match 1+ chars other than a whitespace char or ;

See a regex demo.

const myString = "java=10514;js=237;jsp=3995;web=5;xml=42";
const regex = /\b(java|jsp?|web|xml)=([^;\s]+)/g;
const kv = Object.fromEntries(
  Array.from(
    myString.matchAll(regex), m => [m[1], m[2]]
  )
)
console.log(kv)
console.log(kv.java);

answered Dec 27, 2022 at 9:27

The fourth bird

165k16 gold badges61 silver badges75 bronze badges

6 Comments

RavinderSingh13 Over a year ago

Hey buddy, nice code. Could you please explain it from Object.fromEntries to its completion. Trying to learn JS but not able to fully understand it. I get that you are doing it in 2 capturing groups and putting output into key value pair format but how its working inside JS thing not sure. Will be grateful to you, Thank you.

The fourth bird Over a year ago

@RavinderSingh13 Hey man, yes of course. The Object.fromEntries() transforms a list of key-value pairs into an object The Array.from() creates a new, shallow-copied Array instance from an iterable or array-like object.

The fourth bird Over a year ago

The String.prototype.matchAll() method returns an iterator of all results matching a string against a regular expression, including capturing groups. So matchall returns the iterator with the 2 capture group values to Array.from, which returns an array of arrays which looks like [["java","10514"],["js","237"]] That is a datastructure that Object.fromEntries can process to create an object with key-value pairs.

RavinderSingh13 Over a year ago

Thank you buddy, let me process these comments, thank you for detailed explanation, let us keep these for future users if you ok with it, cheers ++

The fourth bird Over a year ago

@RavinderSingh13 This whole part m => [m[1], m[2]] is a function that is passed as the second parameter to Array.from() as the inline mapping function. The outer square brackets here [...] create an array that will hold the 2 values, where m[1]is the capture group 1 value, and m[2] the capture group 2 value. So we are basically mapping each item of result from matchAll to an array of array's (where each inner array has 2 values)

|

Collectives™ on Stack Overflow

Javascript & regular expression

3 Answers 3

2 Comments

Comments

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related