JavaScript If-Else Tutorial | Conditionals Explained with Code Examples | Beginner Friendly

JavaScript If-Else Tutorial | Conditionals Explained with Code Examples

Conditional statements in JavaScript allow your program to make decisions based on different conditions. This tutorial covers the basics of if, if-else, and if-else if chains, demonstrating how to control the flow of your code with practical examples like age checks and grade calculations.

Code

// Lesson 1: Basic If Statement
const age = 20;
if (age >= 18) {
  console.log("You are an adult.");
}

// Lesson 2: If-Else Statement
const age2 = 16;
if (age2 >= 18) {
  console.log("You are an adult.");
} else {
  console.log("You are a minor.");
}

// Lesson 3: If-Else If Chain (Grade Calculator)
const score = 85;
if (score >= 90) {
  console.log("Grade: A");
} else if (score >= 80) {
  console.log("Grade: B");
} else if (score >= 70) {
  console.log("Grade: C");
} else if (score >= 60) {
  console.log("Grade: D");
} else {
  console.log("Grade: F");
}

// Lesson 4: Testing Multiple Values
const testScores = [95, 82, 67, 58];
for (let i = 0; i < testScores.length; i++) {
  const s = testScores[i];
  if (s >= 90) {
    console.log(s + ": Grade A");
  } else if (s >= 80) {
    console.log(s + ": Grade B");
  } else if (s >= 70) {
    console.log(s + ": Grade C");
  } else if (s >= 60) {
    console.log(s + ": Grade D");
  } else {
    console.log(s + ": Grade F");
  }
}

Key Points

• The if statement executes code only when its condition is true.
• If the if condition is false, an else block can run alternative code.
• Use else if to check multiple conditions in sequence until one matches.
• Conditions are evaluated top to bottom, and only the first true block runs.
• Testing with different inputs helps verify that your conditional logic works correctly.