Introduction to JavaScript

Built-in Objects

In addition to console, there are other objects built into JavaScript. Down the line, you’ll build your own objects, but for now these “built-in" objects are full of useful functionality.

For example, if you wanted to perform more complex mathematical operations than arithmetic, JavaScript has the built-in Math object.

The great thing about objects is that they have methods! Let's call the .random() method from the built-in Math object:

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

In the example above, we called the .random() method by appending the object name with the dot operator, the name of the method, and opening and closing parentheses. This method returns 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 example above will likely evaluate to a decimal. To ensure the answer is a whole number, we can take advantage of another useful Math 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 down 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.

To see all of the properties and methods on the Math object, take a look at the documentation here.

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