Nodejs string search and string parser-CodePudding

I have a string below, and I want to extract the value of the headers inside my string, such as "Change Type" or "Change Summary".

I was thinking about using regex, but I'm not sure because it seems like regex is only used for validations.

" # Release Notes #
 ## Change Type ##
-[] Enhancement
-[x] Defect

## Change Summary ##
This Release is to fix a null pointer issue. 

## Is this Active  ##
-[x] Yes
-[] No

## Team ##
Jaguar Team

## Impacted Customer ##
-[x] Internal
-[] External  "

How can I do this effectively? Can I use regex for this?

CodePudding user response：

We can use Regex with lookarounds to match our data.

const re = /(?<=(^|\n)##  ).*?(?=  ##(\n|$))/g;

const titles = `" # Release Notes #
 ## Change Type ##
-[] Enhancement
-[x] Defect

## Change Summary ##
This Release is to fix a null pointer issue. 

## Is this Active  ##
-[x] Yes
-[] No

## Team ##
Jaguar Team

## Impacted Customer ##
-[x] Internal
-[] External  "
`.match(re);
console.log(titles);

Note this intentionally doesn't match ## Change Type ##, as there is a space in front of it, nor # Release Notes # for the same reason and because it only has one # before and after it.

Regex Breakdown

(
  ?<=(^|\n)            # match any text after a new line or beginning of string
  ##                   # match "##" followed by one or more spaces
)
.*?                    # match any text with greedy-prevention
(
  ?=  ##               # match any text before any one or more spaces and "##"
  (\n|$)               # match anything before a new line or end of string
)

Without regex

If you don't want to use regex because you got mad at it, offended it, or have any other (good) reason not to use it, here's the regex-free alternative.

const extract = input => {
  let strs = input.split("\n"); // split the string line by line
  return strs.map(i => {
    // check if string matches criterion
    if(i.startsWith("## ") && i.endsWith(" ##"))
      return i.substring(3, i.length - 3); // remove "## " and " ##"
  }).filter(o => !!o); // remove falsy values
};

console.log(extract(`" # Release Notes #
 ## Change Type ##
-[] Enhancement
-[x] Defect

## Change Summary ##
This Release is to fix a null pointer issue. 

## Is this Active  ##
-[x] Yes
-[] No

## Team ##
Jaguar Team

## Impacted Customer ##
-[x] Internal
-[] External  "
`));

CodePudding user response：

You can get the headers with: /(?<=##). (?=##)/g
This pattern basically tells to match anything that is between two #.

Test here: https://regex101.com/r/F4HUIf/1

let input = `" # Release Notes #
 ## Change Type ##
-[] Enhancement
-[x] Defect

## Change Summary ##
This Release is to fix a null pointer issue. 

## Is this Active  ##
-[x] Yes
-[] No

## Team ##
Jaguar Team

## Impacted Customer ##
-[x] Internal
-[] External  "`

let pattern = /(?<=##). (?=##)/g

input.match(pattern).forEach(e=>{
 console.log(e.trim())  //using trim to remove extra white spaces
})

//Change Type
//Change Summary
//Is this Active
//Team
//Impacted Customer