Apart from learning some built-in functions to handle string such as replace and inclues, we are reviving the concept of currying function in JavaScript. Say you want to declare a function with three parameters, you may consider refactoring the code by declaring 3 nested functions, each with one parameter you wish to pass to. Basically, both of them work in the same way. However, noted that only the outerest (the main) function has the name as javaScript in the code above. Both nested (inner) functions are declared without the name. We also use three return keywords in the code.

When executing the function, you then have three () as in the javaScript("I love you")()(). We do not pass any argument into the second and third functions (both are inner/nested functions without the name) and these functions will take the default value we have alreaded declared when being executing.

All in all, we have the final operator return (node + deno + done).length; in which node is "I love you", deno is "love" and done is "I done you". The length of these strings is 24, which you can calculate by yourself the concatenated string I love youyou I done you. Be aware of the empty space, which is also taken into account.