Mastering the else if Statement in JavaScript

The else if statement in JavaScript provides a way to test multiple conditions and execute code based on which condition is true. It allows you to handle more complex decision-making scenarios by sequentially evaluating conditions until one is met or all are skipped.

How the else if Statement Works

The else if statement is used in conjunction with if. When the initial if condition is false, JavaScript checks the else if conditions in order. If none of the conditions are true, the else block (if present) is executed.

Key Points to Remember

1. If the if condition is true, JavaScript will execute its block and skip all else if and else blocks.

2. If the if condition is false, JavaScript evaluates each subsequent else if condition in order until it finds one that is true.

3. If no conditions are true, the else block (if provided) will execute.

Syntax

javascriptCopyEditif (condition1) {
    // Code to execute if condition1 is true
} else if (condition2) {
    // Code to execute if condition2 is true
} else if (condition3) {
    // Code to execute if condition3 is true
} else {
    // Code to execute if none of the above conditions are true
}

Example 1: Checking Voting Eligibility

Let’s determine if a person is eligible to vote:

javascriptCopyEditlet age = 14;

if (age >= 18) {
    console.log("You are eligible to vote.");
} else if (age < 18 && age > 10) {
    console.log("You are not eligible to vote yet.");
} else if (age <= 10) {
    console.log("You are too young to vote.");
}

Output when age = 19:

cssCopyEditYou are eligible to vote.

Output when age = 14:

cssCopyEditYou are not eligible to vote yet.

Example 2: Grading System

Determine a student’s grade based on marks:

Code

javascriptCopyEditlet marks = 75;

if (marks >= 80) {
    console.log("A+");
} else if (marks >= 60) {
    console.log("A");
} else if (marks >= 33) {
    console.log("B");
} else {
    console.log("F");
}

Output when marks = 89:

cssCopyEditA+

Output when marks = 45:

cssCopyEditB

Example 3: Seasonal Weather Checker

Let’s determine the season based on the month:

javascriptCopyEditlet month = "april";

if (month === "january" || month === "february") {
    console.log("Winter is here.");
} else if (month === "april" || month === "may") {
    console.log("Summer is here.");
} else if (month === "october" || month === "november") {
    console.log("Autumn is here.");
} else {
    console.log("Invalid month input.");
}

Output when month = "april":

csharpCopyEditSummer is here.

Enhancements to else if Statements

1. Dynamic Inputs: Use the prompt() method in a browser to allow real-time user input for conditions.

2. Switch Statements: For fixed values, a switch statement can be more concise and readable.

3. Chaining Conditions: Combine conditions using logical operators (&&, ||) to reduce redundancy.