Javascript Statements

What is a JavaScript Statement?

A JavaScript statement is an individual instruction designed to perform a specific action, like declaring a variable or displaying information. When a statement is completed, it is commonly followed by a semicolon (;). These instructions, when combined, form the code necessary to drive your web applications.

var greeting = 'Hello, world!';alert(greeting);

Types of JavaScript Statements

JavaScript comprises various types of statements, each having unique functions. Here are some common types:

• Variable Declaration: Used to declare variables, e.g., var, let, const.
• Conditional Statements: Execute code based on conditions, e.g., if, else, switch.
• Loops: Automate repetitive tasks, e.g., for, while, do-while.
• Functions: Define reusable blocks of code, e.g., function.
• Expression Statements: Evaluate expressions that result in values.
• Return Statement: Specify the value a function should return.

Understanding Javascript Conditional Statement

In JavaScript, conditional statements are crucial constructs that allow you to execute code differently based on the conditions you specify. These statements enable your web applications to make decisions and perform actions accordingly.

Javascript If Statement

The if statement is one of the most fundamental conditional statements in JavaScript. It evaluates a given condition, and if the condition evaluates to true, the code block associated with the if statement executes.

• Syntax: It begins with the keyword if followed by a condition in parentheses () and a code block inside curly braces {}.
• Use else to execute an alternative code block if the condition is false.
• Use else if to check multiple conditions.

var score = 85;if (score > 70) {  console.log('Pass');} else {  console.log('Fail');}

Javascript Switch Statement

The switch statement is another conditional statement in JavaScript, offering a more readable way of evaluating expressions against a set of possible values. This statement is particularly useful for comparing the same expression with different values.

• Syntax: It begins with the keyword switch followed by an expression in parentheses (). The possible case values are defined within curly braces {}.
• Each case represents a potential value of the expression, followed by a colon : and the code block to execute.
• The optional default case executes when the expression doesn't match any case.

var day = 3;switch (day) {  case 1:    console.log('Monday');    break;  case 2:    console.log('Tuesday');    break;  case 3:    console.log('Wednesday');    break;  default:    console.log('Another day');}

Looping with Javascript Statements

Looping is a fundamental concept in programming that allows you to repeat a block of code multiple times. JavaScript offers several looping constructs to make repetitive tasks easier and more efficient. Among them, the For and While loops are commonly used.

For Statement Javascript

The for statement in JavaScript is a powerful tool that allows you to iterate over a sequence of numbers, arrays, or objects. It's an ideal choice when you know in advance how many times you want to loop through a block of code.

• The syntax consists of three parts inside the loop's parentheses: initialization, condition, and increment.
• The loop begins with the for keyword, then it executes the code block as long as the specified condition is true.
• Updates the loop variable in the increment section.

for (var i = 1; i <= 5; i++) {  console.log(i);}

While Statement Javascript

The while statement is another looping mechanism in JavaScript, suitable when the number of iterations isn't predetermined. It continuously executes the associated code block as long as the specified condition remains true.

• Syntax: It starts with the while keyword, followed by a condition in parentheses and a block of code.
• Can lead to infinite loops if the condition never evaluates to false, so handle the loop control judiciously.
• Does not automatically include an iteration expression, so this must be managed within the loop.

var count = 0;while (count < 5) {  console.log(count);  count++;}

Practical Javascript Statement Examples

JavaScript statements form the foundation of any script. These statements help you define the flow, functionality, and interactivity of your web applications. Here, you'll find practical examples of using different types of JavaScript statements effectively.

Variable Declaration in JavaScript

Variables are fundamental components in JavaScript used for storing data. You declare variables using statements such as var, let, and const. Here are examples of each:

• var: For general use across different scopes.

  var name = 'Alice';

• let: Useful for block-scoped variable declarations.

  let age = 30;

• const: For declaring constants, meaning their values can't be reassigned.

  const PI = 3.14;

const MAX_USERS = 100;console.log('Max users: ' + MAX_USERS);

Control Statements in JavaScript

Control statements direct the flow of execution in programs. Common control structures include if, else if, else, and switch statements.

var temperature = 32;if (temperature <= 32) {  console.log('It is freezing');} else {  console.log('It is not freezing');}

Looping Constructs in JavaScript

Loops are essential for repeating tasks, making them vital for operations involving arrays or collections. Two frequently used loop types are for and while loops.

for (var j = 0; j < 10; j++) {  console.log(j);}

Function Declarations in JavaScript

Functions in JavaScript allow you to create reusable blocks of code that perform specific tasks. They make your code modular and easier to maintain.

function greet() {  console.log('Hello!');}greet();