Convert slug variable to title text with javascript

I would advise you to use regular expression. But if you really don't want to use regular expressions, the solution below would work for simple cases. Feel free to modify it as you like it.

function makeTitle(slug) {
  var words = slug.split('-');

  for (var i = 0; i < words.length; i++) {
    var word = words[i];
    words[i] = word.charAt(0).toUpperCase() + word.slice(1);
  }

  return words.join(' ');
}

console.log(
  makeTitle("athlete-profile")
)

function titleize(slug) {
  var words = slug.split("-");
  return words.map(function(word) {
    return word.charAt(0).toUpperCase() + word.substring(1).toLowerCase();
  }).join(' ');
}

console.log(titleize("athlete-profile"))

It works pretty simply:

• It splits the string by - into words.
• It maps each word into title case.
• It joins the resulting words with spaces.

The makeTitle() part of your question can be implemented something like this:

function makeTitle(thisID) {
  return thisID.replace(/-/g, " ").replace(/\b[a-z]/g, function() {
    return arguments[0].toUpperCase();
  });
}

console.log(makeTitle("athlete-profile"))

The first .replace() changes all hyphens to spaces, and then the second .replace() takes any lower-case letter that follows a word boundary and makes it upper-case.

(For more information see the MDN doco for .replace().)

As far as doing it without using regular expressions, I'm not sure why you'd specifically want to avoid them, especially when the required expressions are pretty simple in this case (especially if you do the hyphen to space and first letter capitalisation in two steps as shown above). But there are endless ways to do this without regex using various combinations of JavaScript's string manipulation methods.