Extracting parts of the string between two special character - Javascript

Question

I have a complex string which i get as a part of my response. but i need to extract parts of strings between special characters i.e starting special character -> and ending special character <-. Anything between these tags needs to be displayed rest should be ignored

String to be changed

"validation error [claimDto:Reporter.HomeNumber->Value entered must be a valid phone number<-, claimDto:Lobs.PostalCode->Please enter a valid ZIP code.<-, claimDto:Lobs.HomeNumber->Value entered must be a valid phone number]"

Expected Value:

Value entered must be a valid phone number
Please enter a valid ZIP code.

I don't think this question is a duplicate. The linked question deals with single-character delimiters (like "[" and "]") and that solution won't work with the multi-character delimiters in this question (like "->" and "<-") so it makes sense for this to stay open as its own question. — Sly_cardinal, Nov 08 '18 at 08:12

CertainPerformance · Answer 1 · 2018-11-08T06:16:24.087

2

A simple match would do it, lookbehind for ->, lookahead for <-, and use a global flag:

const input = "validation error [claimDto:Reporter.HomeNumber->Value entered must be a valid phone number<-, claimDto:Lobs.PostalCode->Please enter a valid ZIP code.<-, claimDto:Lobs.HomeNumber->Value entered must be a valid phone number]";
console.log(input.match(/(?<=->).*?(?=<-)/g));

Some browsers don't support lookbehind yet - without using lookbehind, match the opening arrow instead of lookbehind, iterate over every match and extract the group:

const input = "validation error [claimDto:Reporter.HomeNumber->Value entered must be a valid phone number<-, claimDto:Lobs.PostalCode->Please enter a valid ZIP code.<-, claimDto:Lobs.HomeNumber->Value entered must be a valid phone number]";
let match;
const re = /->(.*?)(?=<-)/g;
const output = [];
while (match = re.exec(input)) {
  output.push(match[1]);
}
console.log(output);

edited Nov 08 '18 at 06:16

answered Nov 08 '18 at 06:12

CertainPerformance

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The snippet's giving an error. – vibhor1997a Nov 08 '18 at 06:15
Sounds like your browser doesn't support lookbehind, it's new-ish, iterate over the matches manually instead – CertainPerformance Nov 08 '18 at 06:16
yes, I found out its not supported in firefox till now. Its a ES2018 feature. – vibhor1997a Nov 08 '18 at 06:18

score 0 · Answer 2 · answered Nov 08 '18 at 06:41

You can get close to @CertainPerformance's answer without needing lookbehind support:

const input = "validation error [claimDto:Reporter.HomeNumber->Value entered must be a valid phone number<-, claimDto:Lobs.PostalCode->Please enter a valid ZIP code.<-, claimDto:Lobs.HomeNumber->Value entered must be a valid phone number]";

const matchText = /->(.+)/;
input.split('<-')
    .map(s => matchText.exec(s))
    .filter(x => x)
    .map(x => x[1]);

Result:

[
    "Value entered must be a valid phone number",
    "Please enter a valid ZIP code.",
    "Value entered must be a valid phone number]"
]

Is your input string missing a final <-? That's what's causing the trailing ] character ;)

Explanation:

input.split('<-')   // split the string into segments that end with '<-' (removes the '<-' characters too)

.map(s => /->(.+)/.exec(s))    // capture any text after '->' to the end of the string. Any strings without '->' in them will not match and will return null

.filter(x => x) // filter out any null regexp results    

.map(x => x[1]); // put out the captured text from each regexp result (x[0] is the entire match, x[1] is just the captured text)

Extracting parts of the string between two special character - Javascript

2 Answers2