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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 (inclusive) and 1 (exclusive).

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:

`Math.random`

generates a random number between 0 and 1.- We then multiply that number by
`50`

, so now we have a number between 0 and 50. - Then,
`Math.floor()`

rounds the number down to the nearest whole number.

If you wanted to see the number printed to the terminal, you would still need to use a `console.log()`

statement:

`console.log(Math.floor(Math.random() * 50)); // Prints a random whole number between 0 and 50`

To see all of the properties and methods on the `Math`

object, take a look at the documentation here.

Inside of a `console.log()`

, create a random number with `Math.random()`

, then multiply it by `100`

.

Now, use `Math.floor()`

to make the output a whole number.

Inside the `console.log()`

you wrote in the last step, put the existing `Math.random() * 100`

code inside the parentheses of `Math.floor()`

.

Find a method on the JavaScript `Math`

object that returns the smallest integer greater than or equal to a decimal number.

Use this method with the number `43.8`

. Log the answer to the console.

Use the JavaScript documentation to find a method on the built-in `Number`

object that checks if a number is an integer.

Put the number `2017`

in the parentheses of the method and use `console.log()`

to print the result.