Function that replaces the wrapped word with ampersands with just single hashtag at start

I tried to write a function to replace ampersands which are arround word in string with just single hashtag which will be at the beginning of word &word& => #word. And I did it, but after looking at my code I can tell that it’s kind of ugly, and also I need function that will return text to version with ampersands too. So, maybe someone can tell me how can I improve it? Maybe someone can provide version with regex?

const text = "&string& someText&string2& &string3& &string4&&string5&";

const replaceAmpersandsWithHashtag = (text: string) => {
    const firstStep = text.replace(/\&/g, '#');
    let occurenceOfHashtag = 0;
    const secondStep = firstStep.split('').filter(char => {
      if(char === '#') {
        occurenceOfHashtag += 1 ;
        return occurenceOfHashtag % 2 === 0 ? false : true;
      }
      return true
      }).join('');
    return secondStep
}

const replaceHashtagWithAmpersands = (text: string) => {
    const firstStep = text.replace(/\#/g, '&');
    let isLookingForNextAmpersand = false;
    const secondStep = firstStep.split('').map((char, index) => {
      if(char === '&') {
        isLookingForNextAmpersand = true;
        return char;
      }
      if(isLookingForNextAmpersand && firstStep.length === index + 1) {
        isLookingForNextAmpersand = false;
        return `${char}&`
      }
      if(isLookingForNextAmpersand && (firstStep.charAt(index + 1) === ' ' || firstStep.charAt(index + 1) === '&')) {
        isLookingForNextAmpersand = false;
        return `${char}&`
      }
      return char
      }).join('');
    return secondStep
}

const textWithHastags = replaceAmpersandsWithHashtag(text);
const againWithAmpersands = replaceHashtagWithAmpersands(textWithHastags);

// Should be "#string someText#string2 #string3 #string4#string5"
console.log(textWithHastags)
// Should be "&string& someText&string2& &string3& &string4&&string5&"
console.log(againWithAmpersands)
// Should be "true"
console.log(text === againWithAmpersands)

>Solution :

Use a capture group in the regexp to copy the word between the & to the replacement.

function replaceAmpersandsWithHashtag(string) {
  return string.replace(/&(\w+)&/g, '#$1');
}

function replaceHashtagWithAmpersands(string) {
  return string.replace(/#(\w+)/g, '&$1&');
}

const text = "&string& someText&string2& &string3& &string4&&string5&";

const textWithHastags = replaceAmpersandsWithHashtag(text);
const againWithAmpersands = replaceHashtagWithAmpersands(textWithHastags);

// Should be "#string someText#string2 #string3 #string4#string5"
console.log(textWithHastags)
// Should be "&string& someText&string2& &string3& &string4&&string5&"
console.log(againWithAmpersands)
// Should be "true"
console.log(text === againWithAmpersands)