Learn how to use addition, subtraction, multiplication, division, powers, rounding, modulo and more in this article…

Getting started!

Welcome to another post on Code The Web! First of all, I want to encourage you to follow along in this article. It will help you learn better, and also help you to remember what you have done. Let’s start by making a new HTML file with a <script> tag in it:

<!DOCTYPE html>
<html>
    <head>
        <title>JavaScript Math</title>
    </head>
    <body>
        <h1>JavaScript :)</h1>
        <script>
            // Our script will go here!
        </script>
    </body>
</html>

Once that’s done, open it up in your web browser and you’re ready to go! (don’t forget to save and reload the page every time you make a change)

Types of numbers

There are two main types of numbers in JavaScript: floats and integers. Integers are whole numbers without decimals. Here are a few examples:

  • 3
  • 0
  • 156

Floats are numbers which contain a decimal. It is important to note that floats can be whole numbers. Wait whaaat? I thought you said that integers were whole numbers? Well, stuff like 5.0 is still considered a float, because it has a decimal and could be 5.1.

  • 2.225345
  • 0.0
  • 42.0

For the most part, you won’t have to worry about these different types because JavaScript will automatically convert them for you (😍). However, in some programming languages, you will have to do it yourself. There are also some cases in JavaScript where you will have to work with converting stuff between floats and integers.

Basic operators

Let’s start right from the beginning - with the basic operations!

Addition

Addition in JavaScript is really simple - all you need to do is put a plus sign between two numbers, just like in real life. Try it out! Add the following to your script, save, then reload the page:

alert(1 + 2);
// Equal to 3
alert(2.5 + 3.5);
// Equal to 6
alert(-2 + -3);
// Equal to -5

You can also add floats and integers in the one expression:

alert(7 + 1.25);
// Equal to 8.25

Obviously, the number that is returned will be a float. Moving on!

Subtraction

Subtraction also works just as it does in real life. Easy, huh? Here are some examples - you can try them out if you want:

alert(5 - 3);
// Equal to 2
alert(33 - 42);
// Equal to -9
alert(-3.3 - 1.1);
// Equal to -4.4

Multiplication

Multiplication is slightly different to how you would do it on paper. Normally, we would just use a cross symbol - the letter x on a keyboard. However, we can’t use that! In programming, we try to give each character only one meaning. Since x is already a letter, we have to use something else. In JavaScript, we use the asterisk (*) symbol. Here are some examples of multiplication in JavaScript:

alert(1 * 3);
// Equal to 3
alert(9 * 8);
// Equal to 72
alert(-2.23 * 7.92);
// Equal to -17.6616
alert(-4 * -3);
// Equal to 12

Division

Division also works differently to on paper. While there is a Unicode symbol for division (÷), it is not something that you can type easily on your keyboard and is not that commonly used. Instead, we use the slash (/) sign to mean ‘divided by’. Here are some examples:

alert(1 / 2);
// Equal to 0.5
alert(20 / -4);
// Equal to -5
alert(0 / 5);
// Equal to 0
alert(64 / 0);
// Equal to Infinity

I just want to highlight the last one on that list:

alert(64 / 0);
// Equal to Infinity

In maths, anything divided by 0 is equal to infinity (explanation here). However, in JavaScript it can’t equal to “infinity” - otherwise JavaScript would think it was a variable! So, we need to capitalize it to make it Infinity. This is a special value in JavaScript (not a variable). It doesn’t really have many use cases but is the outcome of statements like the one above.

Fun fact: Infinity - Infinity in JavaScript does not equal 0!

Modulo

Modulo is something that you may not have heard of before, unlike the four operations above. Put simply, modulo is the remainder when dividing two numbers. It is done by putting a % sign between the two numbers. For example:

alert(24 % 5);
// Equal to 4

Let’s break it down a bit further. We have the numbers 24 and 5, separated by the modulo (%) sign. This means that to calculate the answer in our heads, we’d first need to divide 24 by 5 (into groups of five). Here, we can make four groups of five. However, we’d still have an extra 4 left over as a remainder. So, the answer is 4. Here are some other examples - if you still don’t get it, try and do the process above on these:

alert(10 % 4);
// Equal to 2
alert(30 % 3);
// Equal to 0, 3 goes into 30 ten times without a remainder
alert(6 % 5);
// Equal to 1

Math functions

As well as the operators above, there are also some functions that we can use to carry out slightly more advanced tasks. These functions generally follow the form of Math.whateverTheFunctionIs(). This is because Math is an object containing lots of different math-related functions. I’ll talk more about objects in a later article, but you don’t really have to worry about how it works for the moment. Just use the syntax that I put here and you’ll be fine.

To the power of

We do this using the Math.pow(number,power) function. For example, let’s say we wanted to square the number 5:

alert(Math.pow(5,2));
// Equal to 25

Wait whaaat? A function inside the alert function? Yup. This is because Math.pow is a function that returns something. You can think of it just like a variable. So instead of x being equal to 25, Math.pow(5,2) is equal to 25.

You can also go to higher powers if you want (pun intended 🙏 *sigh*):

alert(Math.pow(3,3)); // 3 to the power of 3
// Equal to 27
alert(Math.pow(2,10)); // 2 to the power of 10
// Equal to 1024

Square root & Cube root

You can calculate square an cube roots in JavaScript using the Math.sqrt() and Math.cbrt() functions. Here are some examples which you can try out:

alert(Math.sqrt(25));
// Equal to 5
alert(Math.cbrt(8));
// Equal to 2

Rounding

We can round a number to a whole number using the Math.round() function. Here are some examples:

alert(Math.round(35.82562));
// Equal to 36
alert(Math.round(35.22353));
// Equal to 35
alert(Math.round(4));
// Equal to 4 (already rounded)
alert(Math.round(6.5));
// Equal to 7 (.5 rounds up)

It will round up if the decimal part of the number is greater than or equal to 0.5. Otherwise it will round down.

Specifically rounding up or down

But what if we want to specifically round up or down? For example, what if before we wanted to round 35.82562 downwards? This is where floor and ceiling come in handy. Math.floor() rounds the number down no matter what, while Math.ceil() rounds the number up no matter what. Note that Math.ceil(6) or even Math.ceil(6.0) would not round up to 7. Here are some examples:

alert(Math.floor(35.82562));
// Equal to 35
alert(Math.ceil(35.82562));
// Equal to 36
alert(Math.ceil(4.0));
// Equal to 4
alert(Math.ceil(4.01));
// Equal to 5
alert(Math.floor(0.99999));
// Equal to 0

Conclusion

That’s it for today! This just covered some basic math operations, but there are many more. Click here for a list of all the functions in the Math object (the ones that start with Math.). As well as having functions, the Math object also has some static values such as Math.PI - they are listed on that page as well.

Hopefully, you learned a lot from this article! If you did, I’d be stoked if you shared it on social media.

Also, it takes me a lot of time to write these articles. So far I’ve spent 1 hour and 45 minutes on this article, and I spend over 3 hours on some articles! At the time of writing, I currently don’t have any ads on here, so the only way that I can get support for all this content is via donations.

If you want to give me a little thanks and make my entire day feel awesome, I’d really appreciate if you’d buy me a coffee ☕. It’s only $4, and it makes a big difference. In fact, at the moment I’m only 49 cents short of covering my costs for Code The Web, and it would be really cool if you were the one to help me reach that milestone. Okie, enough about that 😉

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That’s it for today! Next time, I’ll be writing about for loops and while loops in JavaScript - they are really cool, because you can tell the browser to repeat bits of your code over and over again (even with different values each time)! See you then 🚀

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