Search and replacing strings without using Regex but loops instead, how can I replace more than one word at a time?

Question

I found a way to do string search and replace without using Regex but when I want to replace more than one instance it does it one out at time instead of all instances at the same time. How can I get the loop to work?

'use strict'

function main() {
  document.addEventListener('DOMContentLoaded', function() {
    document.getElementById('replace').addEventListener('click', replace);
    document.getElementById('replaceAll').addEventListener('click', replaceAll);
  });

}

function replace(evnt) {
  evnt.preventDefault()
  let userText = document.getElementById('input').value;
  let search = document.getElementById('search').value;
  let replaceText = document.getElementById('replaceText').value;
  let caseSensitive = document.getElementById('case').checked;
  document.getElementById('input').value = userText.replace(search, replaceText);

}

function replaceAll(evnt) {
  evnt.preventDefault();
  let userText = document.getElementById('input').value;
  let search = document.getElementById('search').value;
  let replaceText = document.getElementById('replaceText').value;

  for (let r = 0; r < userText.indexOf(search); r++) {
    document.getElementById('input').value = userText.replace(search, replaceText);
    console.log(r);

  }
}

<form id="form">
  <div>
    <textarea id="input" row="10" cols="50" placeholder="Enter text here"></textarea>
  </div>
  <div>
    <input type="text" id="search" name="search">
    <input type="text" id="replaceText" name="replacebox">
  </div>
  <div>
    <input type="checkbox" id="case" name="case sensitivity" />
    <label for="uppercase">case sensitivity</label>
  </div>
  <div>
    <button type="submit" id="replace">Replace</button>
  </div>
  <div>
    <button type="submit" id="replaceAll">Replace all</button>
  </div>
</form>

Answer 1

In

for(let r = 0; r < userText.indexOf(search);r++) {
    document.getElementById('input').value = userText.replace(search, replaceText);
}

On every iteration, you're taking the userText string and replacing one substring inside it. You're not taking the replaced string from the prior iteration; you're taking the original string, so in the end, no more than one replacement, at most, will have been made.

Reassign a variable instead, perhaps userText, then assign to the input after the loop is done:

for(let r = 0; r < userText.indexOf(search);r++) {
    userText = userText.replace(search, replaceText);
}
document.getElementById('input').value = userText;

Could also use .includes, it's more intuitive:

while (userText.includes(search)) {
  userText = userText.replace(search, replaceText);
}

'use strict'

function main() {
  document.addEventListener('DOMContentLoaded', function() {
    document.getElementById('replace').addEventListener('click', replace);
    document.getElementById('replaceAll').addEventListener('click', replaceAll);
  });

}

function replace(evnt) {
  evnt.preventDefault()
  let userText = document.getElementById('input').value;
  let search = document.getElementById('search').value;
  let replaceText = document.getElementById('replaceText').value;
  let caseSensitive = document.getElementById('case').checked;
  document.getElementById('input').value = userText.replace(search, replaceText);

}

function replaceAll(evnt) {
  evnt.preventDefault();
  let userText = document.getElementById('input').value;
  let replaceText = document.getElementById('replaceText').value;
  while (userText.includes(search.value)) {
    userText = userText.replace(search.value, replaceText);
  }
  input.value = userText;
}
const [repButton, repAllButton] = document.querySelectorAll('button');
repButton.onclick = replace;
repAllButton.onclick = replaceAll;

<form id="form">
  <div>
    <textarea id="input" row="10" cols="50" placeholder="Enter text here">abcabc</textarea>
  </div>
  <div>
    <input type="text" id="search" name="search" value="abc">
    <input type="text" id="replaceText" name="replacebox" value="123">
  </div>
  <div>
    <input type="checkbox" id="case" name="case sensitivity" />
    <label for="uppercase">case sensitivity</label>
  </div>
  <div>
    <button type="submit" id="replace">Replace</button>
  </div>
  <div>
    <button type="submit" id="replaceAll">Replace all</button>
  </div>
</form>