Ванильный JavaScript добавляет тег <br> после определенного количества символов в строке

<div id= "customer-comments">
    Customer comment 1 - Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin in ligula neque. Aenean urna nisi, rutrum ac neque eu, aliquet aliquam ligula. Customer comment 2 - Etiam venenatis lacus quam, et imperdiet risus tempor quis. Aenean elit justo, fermentum ac leo vel, bibendum mattis est. Vestibulum sed condimentum mi, id ullamcorper libero
</div>
<br>
<p>Split Up:</p>
<br>
<div id = "div2"></div>

<script>
    function chunk(str, n) {
        var ret = [];
        for(var i = 0; i < str.length; i += n) ret.push(str.substr(i, n))
        return ret;
    };

    let commentsText = document.getElementById('customer-comments').innerText;
    document.getElementById("div2").innerHTML = chunk(commentsText, 120).join('<br>');
</script>

var out = document.querySelector("#foo");
var text = out.textContent;
var str = text.replace(/(.{10})/g, '$1<br/>');
out.innerHTML = str;

<div id = "foo">1234567890123456789012345678901234567890123456789012345678901234567890</div>

var max = 120;    // Number of letters
var str = '<br>'; // Add <br> tag or something else

var wrapEl = document.getElementById('customer-comments');
var w = wrapEl.innerText.split(' ');
var sum = 0;
var comp = 0;
var l = 0;
for (let i = 0; i < w.length; i++) {
    sum = w[i].length + sum;
    if (sum >= max) { w.splice(l, 0, str); sum = 0; comp = 0; } else { comp = sum; l = i + 1; }
}

wrapEl.innerHTML = w.join(' ');

<div id = "customer-comments">
    Customer comment 1 - Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin in ligula neque. Aenean urna
    nisi, rutrum ac neque eu, aliquet aliquam ligula. Customer comment 2 - Etiam venenatis lacus quam, et imperdiet
    risus tempor quis. Aenean elit justo, fermentum ac leo vel, bibendum mattis est. Vestibulum sed condimentum mi,
    id ullamcorper libero
</div>

var str = "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum. Why do we use it? It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like)."
var x = 0;
var newStr  = ""
for(var i = 0; i < str.length; i++){
  if (x == 120){
    newStr + = "<br>"
    x=0
  }
  newStr += str[i]
  x++;
}
console.info(newStr)

// get the str using textContent
var str = document.getElementById('str');
// function that runs a for loop and checks if the character
// counted in that string exceeds a given number (num), if so
// push the result of the loop between the remainder and num // into an array value repeat this process. 
// Loop over the resulting array and create span tags for each
// value within the arr. Assign a class that displays as a 
// block level element, affectively creating a new line. 
function formatStr(str, num, el, attr) {
  var result = [];
  for (var i = 0; i < str.length; i += num) {
    result.push(str.substr(i, num));
  }
  var output = '';
  for (let j in result) {
    output += `<${el}${attr}>${result[j]}</${el}>`;
  }
  return output;
}
// reset the original displayed div to the newly formatted
// span elements with 10 characters per line
// and add a class block-level with a block display
document.getElementById("str").innerHTML = formatStr(str.textContent, 10, 'span', ' class = "block-level"');
// display the original string reformtted to div elements 
// with 20 characters per line and add a class of
// yellow-bg
document.getElementById("results").innerHTML = formatStr(str.textContent, 20, 'div', ' class = "yellow-bg"');
// display the original string with 5 perline to p tags
// with no added class
document.getElementById("results2").innerHTML = formatStr(str.textContent, 5, 'p', '');

.block-level {
  display: block;
}

.yellow-bg {
  background-color: yellow;
  padding: 5px;
  margin-bottom: 3px;
}

<div id = "str">1234567890123456789012345678901234567890123456789012345678901234567890</div>


<div id = "results"></div>
<div id = "results2"></div>