var yourString = "The quick brown fox jumps over the lazy dog"; //replace with your string.
var finalString = "";
var maxLength = 16 // maximum number of characters to extract
var count = 0;
var maxTries = ((yourString.length / maxLength) * 2);

while (yourString.length > maxLength) {
  count++;
  if (count > maxTries) {
    break;
  }
  //trim the string to the maximum length
  var trimmedString = yourString.substr(0, maxLength);
  
  //re-trim if we are in the middle of a word
  trimmedString = trimmedString.substr(0, Math.min(trimmedString.length, trimmedString.lastIndexOf(" ")));
  
  yourString = yourString.replace(trimmedString + " ", "");
  
  finalString += trimmedString + '<br>';
}

finalString += yourString;

console.log(yourString);
console.log(finalString);