JavaScript Syntax - JavaScript Tutorial

JavaScript Statements

JavaScript statements are instructions to be executed by the browser. They can perform actions like displaying output, making calculations, or manipulating the DOM. Each statement is usually separated by a semicolon (;).

Explanation of Code:

Each line in the example below is a JavaScript statement. The last statement uses console.log to output the value of z.

let x = 5;
let y = 6;
let z = x + y;
console.log(z);  // Output: 11

JavaScript
​x
 
let x = 5;let y = 6;let z = x + y;console.log(z);  // Output: 11

Case Sensitivity

JavaScript is case-sensitive, meaning myVariable and myvariable are considered two different variables.

Explanation of Code:

The example demonstrates that myVariable and myvariable are treated as separate variables.

let myVariable = 5;
let myvariable = 10;
console.log(myVariable);  // Output: 5
console.log(myvariable);  // Output: 10

JavaScript
 
let myVariable = 5;let myvariable = 10;console.log(myVariable);  // Output: 5console.log(myvariable);  // Output: 10

Whitespace and Indentation

JavaScript ignores extra spaces, tabs, and newlines, which means you can format your code for better readability without affecting its execution.

Exaplanation of Code:

The code uses indentation and spaces to make it more readable.

let a = 5;
let b = 10;
let c = a + b;
console.log(c);  // Output: 15

JavaScript
 
let a = 5;let b = 10;let c = a + b;console.log(c);  // Output: 15

JavaScript Keywords

Keywords are reserved words that have special meaning in JavaScript. They are used to perform specific actions. Examples include var, let, const, if, else, for, while, function, and return.

let name = "John";  // 'let' is a keyword used to declare variables
if (name === "John") {
    console.log("Hello, John!");  // 'if' and 'else' are keywords used for conditional statements
}

JavaScript
 
let name = "John";  // 'let' is a keyword used to declare variablesif (name === "John") {    console.log("Hello, John!");  // 'if' and 'else' are keywords used for conditional statements}

JavaScript Syntax Example Code

Explanation of Code:

Variables: Declared using let.
Comments: Used both single-line and multi-line comments.
Statements: Each statement ends with a semicolon.
Output: console.log displays the result in the console.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>JavaScript Syntax Example</title>
</head>
<body>
    <script>
        // Declare variables
        let a = 5;
        let b = 10;

        /*
          Calculate the sum
          and display the result
        */
        let sum = a + b;
        console.log("The sum is " + sum);  // Output: The sum is 15
    </script>
</body>
</html>

HTML
 
<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <meta name="viewport" content="width=device-width, initial-scale=1.0">    <title>JavaScript Syntax Example</title></head><body>    <script>        // Declare variables        let a = 5;        let b = 10;​        /*          Calculate the sum          and display the result        */        let sum = a + b;        console.log("The sum is " + sum);  // Output: The sum is 15    </script></body></html>

JavaScript Statements

Case Sensitivity

Whitespace and Indentation

JavaScript Keywords

JavaScript Syntax Example Code

JavaScript Labs