Drag the edges to resize the window.

In Projects, you can keep track of your progress as you go throught the tasks. Check each item as you complete it!

Code Editor
Learn
Introduction to JavaScript

Libraries

Instance methods, by definition, require that you create an instance before you can use them. What if you want to call a method without an instance? That's where JavaScript libraries come in. Libraries contain methods that you can call without creating an instance.

One such collection contains mathematical methods, aptly named the Math library.

Let's see how you call the .random() method from the Math library:

console.log(Math.random()); // random number between 0 and 1

In the example above, we called the .random() method by appending the library name with a period, the name of the method, and opening (() and closing ()) parentheses. This method returns a random number between 0 and 1. This code prints a random number between 0 and 1.

To generate a random number between 0 and 50, we could multiply this result by 50, like so:

Math.random() * 50;

The answer in the example above will most likely be a decimal. To ensure the answer is a whole number, JavaScript provides a built-in method called Math.floor(). Math.floor() takes a decimal number, and rounds down to the nearest whole number. You can use Math.floor() to round a random number like this:

Math.floor(Math.random() * 50);

In this case:

  1. Math.random generates a random number between 0 and 1.
  2. We then multiply that number by 50, so now we have a number between 0 and 50.
  3. Then, Math.floor rounds the number down to the nearest whole number.
Report a Bug
If you see a bug or any other issue with this page, please report it here.