Variables let you store and reuse values in your programs.

Note

A variable is like a container that can hold numbers, text, or more complex data.

Defining Variables

Use the let keyword to create a variable:

let variableName;

Note

Variable names should follow camelCase (first word lowercase, next words capitalized).

A newly created variable has the value undefined, meaning no value has been assigned yet.

You can assign a value later:

let x;
x = 5;

Or assign it immediately:

let x = 13;

Using Variables

Variables help avoid repeating the same value in your code:


              1234
            
let word = "VariableText";  // The variable value is the `"VariableText"`

console.log("ValueText");  // Print the `"ValueText"`
console.log(word);  // Print the variable value

You can reassign values anytime:


              123456
            
let numb;
numb = 100;
console.log(numb);

numb = 100 + 20;
console.log(numb);

Why Variables Matter

Without variables, you would have to rewrite the same value many times and fix every occurrence if there's a typo.

Example with repeated text:


              1234
            
console.log("Hello Word!");
console.log("I love this Word!");
console.log("I need to live in this Word!");
console.log("This Word is the best!");

Using a variable makes fixes easier:


              123456
            
let x = "Word";

console.log("Hello " + x + "!");
console.log("I love this " + x + "!");
console.log("I need to live in this " + x + "!");
console.log("This " + x + " is the best!");

Change "Word" to "World" once, and all lines update.

Note

This uses string concatenation, which you’ll learn next.

Note

In the example above, we used string concatenation. We will delve into string concatenation in the next section.

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Section 2. Chapter 1

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Variables let you store and reuse values in your programs.

Note

A variable is like a container that can hold numbers, text, or more complex data.

Defining Variables

Use the let keyword to create a variable:

let variableName;

Note

Variable names should follow camelCase (first word lowercase, next words capitalized).

A newly created variable has the value undefined, meaning no value has been assigned yet.

You can assign a value later:

let x;
x = 5;

Or assign it immediately:

let x = 13;

Using Variables

Variables help avoid repeating the same value in your code:


              1234
            
let word = "VariableText";  // The variable value is the `"VariableText"`

console.log("ValueText");  // Print the `"ValueText"`
console.log(word);  // Print the variable value

You can reassign values anytime:


              123456
            
let numb;
numb = 100;
console.log(numb);

numb = 100 + 20;
console.log(numb);

Why Variables Matter

Without variables, you would have to rewrite the same value many times and fix every occurrence if there's a typo.

Example with repeated text:


              1234
            
console.log("Hello Word!");
console.log("I love this Word!");
console.log("I need to live in this Word!");
console.log("This Word is the best!");

Using a variable makes fixes easier:


              123456
            
let x = "Word";

console.log("Hello " + x + "!");
console.log("I love this " + x + "!");
console.log("I need to live in this " + x + "!");
console.log("This " + x + " is the best!");

Change "Word" to "World" once, and all lines update.

Note

This uses string concatenation, which you’ll learn next.

Note

In the example above, we used string concatenation. We will delve into string concatenation in the next section.

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 1

Understanding Variables in JavaScript

Defining Variables

Using Variables

Why Variables Matter

Understanding Variables in JavaScript

Defining Variables

Using Variables

Why Variables Matter