Understanding the if Statement in JavaScript

The if statement is one of the most fundamental control flow structures in JavaScript. It is used to evaluate a condition and execute a block of code if that condition is true. If the condition is false, the code inside the block will not run.

// some code before if condition is work

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What is an if Statement?

The term if literally means "check this condition." In JavaScript, you write the condition inside parentheses ( ), and if it evaluates to true, the code inside the curly braces { } is executed.

For example:

javascriptCopyEditif (condition) {
    // Code to execute if the condition is true
}

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Key Features of the if Statement

• Condition: A condition is an expression that evaluates to either true or false.

• True Execution: If the condition is true, the code block inside the { } is executed.

• False Execution: If the condition is false, the code block inside the { } is skipped.

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Syntax of if

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Examples of if Statements

1. Condition Evaluates to True

javascriptCopyEditlet age = 23; 
if (age >= 18) {
    console.log("You can vote");
}

Output:
You can vote

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2. Condition Evaluates to False

let age = 14 ; 
if (age >= 18){
    console.log("you can vote");
}

Output:
(No output since the condition is false)

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Variables Inside an if Block

You can declare and use variables inside an if block. These variables will only exist within the block's scope.

Example

javascriptCopyEditlet age = 23; 
if (age >= 18) {
    console.log("You can vote");
    let multiplier = 5;
    console.log(multiplier * 5);
}

Output:

CopyEditYou can vote
25

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Multiple if Statements

You can use multiple if statements in a single program to evaluate different conditions.

Example 1

javascriptCopyEditlet age = 23; 
if (age >= 18) {
    console.log("You can vote");
}
if (age < 14) {
    console.log("You are not eligible to vote");
}

Output:
You can vote

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Example 2

javascriptCopyEditlet age = 14; 
if (age >= 18) {
    console.log("You can vote");
}
if (age < 18) {
    console.log("You are not eligible to vote");
}

Output:
You are not eligible to vote

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Real-World Example: User Login

Let's consider a real-world scenario: a website login system. If the username matches the stored name, the user is successfully logged in.

Code

javascriptCopyEditlet firstName = "anmol";
if (firstName === "anmol") {
    console.log(`Welcome, ${firstName}`);
}

Output:
Welcome, anmol

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Best Practices for Using if Statements

1. Use Clear Conditions: Write conditions that are easy to understand. Avoid overly complex expressions.

    javascriptCopyEditif (age > 18 && citizenship === "USA") {
        console.log("You can vote in the USA");
    }
   

2. Avoid Redundant if Blocks: Combine conditions where appropriate.

    javascriptCopyEdit// Instead of:
    if (age > 18) {
        if (citizenship === "USA") {
            console.log("You can vote in the USA");
        }
    }
   
    // Use:
    if (age > 18 && citizenship === "USA") {
        console.log("You can vote in the USA");
    }
   

3. Ensure Readable Formatting: Always format your code neatly to make it more readable for others.