20 Minute Methods: Learn 30 JavaScript Methods in 12 days by Rodgers Travis

Author:Rodgers, Travis [Rodgers, Travis]
Language: eng
Format: mobi
Publisher: Travis Media
Published: 2019-01-12T16:00:00+00:00

Day 8: Math.round(), Math.ceil(), Math.floor(), Math.max(), Math.min()

Today we will finish up our numbers portion of the course by looking at Math.

What is this Math you speak about?

Math is a built-in JavaScript object that allows you to perform mathematical tasks on numbers.

Here are five simple Math methods that you will use often:

Math.round(); Math.ceil(); Math.floor(); Math.max(); Math.min();

In fact, you can probably tell what they do by just reading them.

Let's dig now into this brief lesson:

Math.round();

The Math.round() method returns the value of a number rounded to the nearest integer.

Open up a browser and the console (if you are viewing this in a browser, just open up the console under this email). Then type a variable such as:

var number = 12.8;

Hit Enter.

Now lets round:

Enter Math.round(number);

And yep, you get 13.

You can also just enter the number as the argument and get the same outcome like:

Math.round(12.8); <----13

Math.round(12.3); <----12

Now try these numbers out and get a feel for how it rounds to the nearest integer:

12456.33211

192.88111

Great!

Math.ceil(); and Math.floor();

Now for these two just remember this:

The ceiling is up and the floor is down.

Math.ceil() returns a value rounded up to its nearest integer.

Math.floor() returns a value rounded down to its nearest integer.

That's it!

Math.ceil(4.1); <---- 5

Math.floor(4.9); <---- 4

Simple enough.

Math.min() and Math.max()

The min() and max() methods do just what they suggest: They return either the lowest number of the numbers passed to it (min) or the largest number of the numbers passed to it (max).

Math.min(4, 2, 9); <---- will return 2

Math.max(4, 2, 9); <---- will return 9;

Let's try another:

var array = [3, 2, 5.4, 10, 3.2, 11, 20, 1, 0];

Now enter Math.min(array);

What did you get? 0?

Nope, you got NAN.

Why. Well, let's look at the parameters of this method.

Math.min([value1[, value2[, ...]]])

Look at those three dots. With ES2015, we can use this to pass an array. It is called a spread operator. This actually causes the array values to be expanded, or "spread", into the function's arguments.

Try it out:

Math.min(...array);

Math.max(...array);

Great job. And that's all for today. Go and rest your brain because our last four lessons are going to be quite a bit tougher.

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