Applying transformations to strings in JavaScript

Suppose we have the variable num with some number:

javascriptlet num = 12345;

Let's find the number of digits in this number. As you already know, to find the length of a string, you can use the property length.

However, it only works on strings, and when applied to a number, it won't work:

javascriptlet num = 12345;
alert(num.length); // shows undefined

To solve the problem, we convert our number to a string and find the length of this string:

javascriptlet num = 12345;
let str = String(num); // convert our number to a string
alert(str.length);     // find the length of the string

You can not involve the intermediate variable str, but apply the property length immediately to the result of the function String:

javascriptlet num = 12345;
alert(String(num).length); // find the length of the string