Introduction to JavaScript – Variables: Mathematical Assignment Operators

In this lesson, you will learn how to use variables and mathematical operators in JavaScript to calculate new values and assign them to variables. This will include the use of mathematical assignment operators to simplify your code.

Learning Objectives

• Understand basic variable assignment.
• Use mathematical assignment operators to streamline code.
• Increment and decrement variables effectively.

Example

Consider the example below:

let x = 4;
x = x + 1;

In the example above:

1. We create the variable x and assign the value 4 to it.
2. On the next line, x = x + 1 increases the value of x from 4 to 5.

Notice that we had to use the variable x on both sides of the assignment operator (=), which can be redundant and confusing. To address this, JavaScript provides built-in mathematical assignment operators.

Mathematical Assignment Operators

These operators help in calculating a new value and assigning it to the same variable without repeating the variable name. See the examples below:

let x = 4;
x += 2; // x equals 6

let y = 4;
y -= 2; // y equals 2

let z = 4;
z *= 2; // z equals 8

let r = 4;
r++; // r equals 5

let t = 4;
t--; // t equals 3

Explanation:

Addition Assignment (+=): Adds the right operand to the left operand and assigns the result to the left operand.

let x = 4;
x += 2; // x equals 6

Subtraction Assignment (-=): Subtracts the right operand from the left operand and assigns the result to the left operand.

let y = 4;
y -= 2; // y equals 2

Multiplication Assignment (*=): Multiplies the left operand by the right operand and assigns the result to the left operand.

let z = 4;
z *= 2; // z equals 8

Increment (++): Increases the variable value by 1.

let r = 4;
r++; // r equals 5

Decrement (--): Decreases the variable value by 1.

let t = 4;
t--; // t equals 3

Exercise

Using what you have learned, complete the following tasks:

1. Add and assign to molecule:
2. Multiply and assign to particle:
3. Increment assay by 1:

let molecule = 16;
let particle = 18;
let assay = 3;

// Add and assign to molecule below
// Multiply and assign to particle below
// Increment assay by 1

Instructions:

1. Use a mathematical assignment operator to add 16 to the value saved to molecule.
2. Use a mathematical assignment operator to assign particle the value of itself multiplied by 6.02.
3. Use the increment operator to increase the value saved to assay by 1.

Answer Code:

Here is the solution for the exercise above.

let molecule = 16;
let particle = 18;
let assay = 3;

// Add and assign to molecule below
molecule += 16;

// Multiply and assign to particle below
particle *= 6.02;

// Increment assay by 1
assay++;

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