Regarding the regex course - create a variable newText, and assign a replacement string to that variable.

function reformatName(text) {


// This one is a regex, i.e.: it's not any specific value or word/s.
// What this one is saying is: 'match any string that starts with one word, then has a space,
// and then ends with another word'.
    const rawName = /^(\w+)\s(\w+)$/;


// Now this one also, is not any specific word or value.
// This (when and only if used with a regex and the replace method)
// is just saying something like: 'if you provide me a regex in a replace(),
// then I will be the result of swapping the second part and the first one,
// adding a comma and a space in between them' like Dale mentioned.
// Notice that by itself it doesn't do anything, and
// it still does not hold anything else than that string: '$2, $1'.
// Needs to be used with a regex and the replace()
// to have any effect
    const newText = '$2, $1';


// The next line is key. This is the line that actually makes the swap.
// This one states: take rawName (a regex with the pattern above)
// and swap it according to what the newText states.
// Notice the return? Well, since this is a function, it still is not doing anything.
// It is only being defined, but everytime this function is called
// and receives a 'text' arg, it will do to it according to all what we mentioned above. 
    return text.replace(rawName, newText);
}

let string = '5337'
let regex = /(\d*)(\d{2})/
let replacement = '$ $1.$2' // The $ here behaves as an actual dollar sign, 
                            // it's not replacing anything, even if used with replace().
string.replace(regex, replacement)
// Outputs: '$ 53.37'. Notice the literal '$'.
// Try it yourself in the console and you'll see.

/***********/
//NEXT:

//Now, he wanted to have the actual dollar sign together with the price in the output, 
// like '$20.25' (instead of '$ 20.25') for example. So he does:
replacement = '$$1.$2'
string.replace(regex, replacement)
// Outputs '$1.37' instead of '$53.37' like we expected. Wait, what? I hear you say :)

// The reason is $$ is the way to escape the dollar sign.
// Think of this: if you want to display the text '$1' (instead of using it to replace anything)
// how would you do? There you go: That's when you need to escape it.
// Otherwise '$1' will replace it for the first value, not give you literally '$1'.

/***********/
//LAST:

//Now, however, what we want is to achieve the '$53.37' thing, right?
// So this is the way to do that:
replacement = '$$$1.$2'   /* I know that you'll tell me that's a lot of money! :)  */
string.replace(regex, replacement)
// Outputs '$53.37', just like we wanted. Why?
// Because the first two dollar signs will actually display literally a dollar sign,
// and then the remaining ones will perform the replacements of $1 for 53,
// and of $2 for 37.
// Does that feel clearer now?