# Arithmetic Operators LJTT #2

Welcome back to the series, today we will be working through JavaScript Arithmetic Operators. I hope you're as excited as I am to relive elementary school math. Let's start learning!

Before getting started be sure to create a basic-arithmetic-operators.spec.js file in your project directory. This is where we will put all of the new Test Cases.

# Basic Arithmetic Operators

In the table below we list some of the basic operators that exist within the JavaScript Language. I'm sure that you will recognize at least a few of them from your 4th grade math class. Throughout this tutorial we will use this table to prove out their usage in JavaScript.

Given the following variables:

var x = 10;
var y = 3;

Now that we have covered the table, we can begin writing the Test Assertions for each of the operators.

# Addition

Looking at the usage for addition in the chart above if we add two variables that are numbers the result will be the sum of the two numbers. Given this statement let's create our first Test Case description, the addition of two numbers will be their sum.

// test case description goes here
test("the addition of two numbers will be their sum", () => {
 // assertions go here
})

Next, we need to create the variables that we will be adding x and y. The value of these two variables will be 10 and 3 respectively as mentioned above in the example.

// test case description goes here
test("the addition of two numbers will be their sum", () => {
 // assertions go here
 var x = 10;
 var y = 3;
})

With the creation of these variables we can use the addition operator on them to write our Test Assertion, expect x + y toEqual 13.

// test case description goes here
test("the addition of two numbers will be their sum", () => {
 // assertions go here
 var x = 10;
 var y = 3;

 expect(x + y).toEqual(13);
})

Great if you run your tests using the npm test command you should see them all passing.

# Subtraction

The next operator in the chart above is subtraction. When subtracting two variables that are numbers the result will be their difference. Based on the previous statement we can create our Test Case description, the subtraction of two numbers will be their difference.

// test case description goes here
test("the subtraction of two numbers will be their difference", () => {
 // assertions go here
})

Once again we will create the variables to operate on. The values of these two variables will once again be 10 and 3.

// test case description goes here
test("the subtraction of two numbers will be their difference", () => {
 // assertions go here
 var x = 10;
 var y = 3;
})

Finally we add our Test Assertion that we expect x - y toEqual 7, since 10 - 3 = 7.

// test case description goes here
test("the subtraction of two numbers will be their difference", () => {
 // assertions go here
 var x = 10;
 var y = 3;

 expect(x - y).toEqual(7)
})

Great work! That's another operator down, give your Test Cases another run using npm test to prove everything is working.

# Multiplication

On to multiplication, when multiplying two variables that are numbers the result will be the product of the two numbers. We will follow the same logic as the previous Test Cases and create our description the multiplication of two numbers will be their product, the variables, the Test Assertion that we expect x * y toEqual 30.

// test case description goes here
test("the multiplication of two numbers will be their product", () => {
 // assertions go here
 var x = 10;
 var y = 3;

 expect(x * y).toEqual(30)
})

# Division

Division is bit different than the others, when dividing values in JavaScript you will run into something called floating point numbers. Floating point numbers, at a high level, allow us to represent decimal values in JavaScript. For example, if we wanted to represent the value of PI we could assign a variable to the value 3.14.

Back to writing our Test Case we will need to keep in mind that since 10 cannot be evenly divided by 3 the result will be a decimal value. As a result, we expect x/y toEqual 3.3333333333333335 is our Test Assertion. The rest of the test will follow the same rules as all of the others.

// test case description goes here
test("the division of two numbers will be their quotient", () => {
 // assertions go here
 var x = 10;
 var y = 3;

 expect(x / y).toEqual(3.3333333333333335)
})

# Modulus

As mentioned in the chart above the modulus operator, otherwise known as the remainder operator, can be used to obtain remainder from the division of two numbers. In our case, we expect x % y toEqual 1, because the remainder after dividing 10 by 3 will be 1. The rest of the Test Case will follow the same rules as the others.

// test case description goes here
test("the modulus of two numbers will be their remainder", () => {
 // assertions go here
 var x = 10;
 var y = 3;

 expect(x % y).toEqual(1)
})

That's it for the basic arithmetic operators! Be sure to run your Test Cases to make sure they are all passing.

Fantastic work getting through this tutorial, you should now have a basic understanding the basic arithmetic operators of JavaScript. I would recommend changing out some of the numbers, updating your Test Cases, and even adding new ones to solidify these concepts. If you have any questions or feedback feel free to contact me or leave a comment below, and always remember you are the Captain of this Quality Cruise Line.

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