CODEWITHSUNDEEP
javascriptregex
Mathieu
Mathieu

Reputation: 4787

Javascript - Replace a character inside a substring of a string

I have a string like "this/ is an example abc/def/fgh/uio to give you an example"

I'd like to target the longest word and replace on this substring any "/" by a "+".

I manage to identify the longest word and I would know how to replace ALL "/" by a "+" BUT I don't know how to replace the "/" only in the longest word.

Here's what I've got so far

//identify longest word in string
function longestWord(str) {
  var words = str.split(' ');
  return words.reduce(longer);
}
function longer(champ, contender) {
  return (contender.length > champ.length) ? contender: champ;
}

//purely given an exemple, some strigns won't be exactly like this
var text2 = "this/ is an example abc/def/fgh/uio to give you an example"

if (longestWord(text2) > 30 ) {
  text2.replace(/\//g, ' / ');
}

The problem is this will also replace the "/" on the substring "this/", and I don't want that.

How to achieve this?

Upvotes: 0

Views: 269

Answers (2)

OliverRadini
OliverRadini

Reputation: 6467

@CertainPermance's solution is far more elegant (and I think performant) than this, but as I'd written the answer I thought I may as well put it in.

It's fairly similar, in truth, though in this instance we get the index of the word and use that to perform the replace, which at the time of writing I thought was necessary. Now looking at the better solution, I realise such a check is not needed, as the longest word in a string will not feature in any other words, so it's easy and safe to simply perform a replace on it.

const data = "this/ is an example abc/def/fgh/uio to give you an example";

const getLongestWordIndex = stringIn => stringIn
  .split(' ')
  .reduce(
    (prev, curr, i) => curr.length > prev.length ? {
      index: i,
      length: curr.length
    } : prev,
    {
      length: -1,
      index: -1
    }
  ).index

const replaceLongestWord = (sentence, replacer) => {
  const longestWordIndex = getLongestWordIndex(sentence);
  const words = data.split(' ');

  return Object.values({
    ...words,
    [longestWordIndex]: replacer(words[longestWordIndex])
  }).join(' ')
}

const wordReplaceFunction = word => word.replace(/\//g, '+')

const result = replaceLongestWord(data, wordReplaceFunction);

console.dir(result)

Upvotes: 1

CertainPerformance
CertainPerformance

Reputation: 370739

Your longestWord function returns the longest word in the string, so you can pass that string alone (not a regular expression) as the first argument to .replace, and replace with (the second argument) the /\//g called on that longest word:

function getLongestWord(str) {
  var words = str.split(' ');
  return words.reduce(longer);
}
function longer(champ, contender) {
  return (contender.length > champ.length) ? contender: champ;
}

var text2 = "this/ is an example abc/def/fgh/uio to give you an example"

const longestWord = getLongestWord(text2);
const output = text2.replace(longestWord, longestWord.replace(/\//g, '+'));
console.log(output);

Upvotes: 9

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