JavaScript Conditional Statements

JavaScript conditional statements are used to execute a block of code based on a specific condition.

if statement

The if statement executes a block of code if a specified condition is true.

if (condition) {
  // code to be executed if condition is true
}


// example
let age = 10;
if (age < 18) {
  console.log("Person is a child");
}

if-else

A separate block of code can be executed if the condition is false:

if (condition) {
  // code to be executed if condition is true
} else {
  // code to be executed if condition is false
}


// example
let age = 10;
if (age < 18) {
  console.log("Person is a child");
} else {
  console.log("Person is an adult");
}

if-else-if

if-else statements can be "chained" to satisfy multiple conditions:

if (condition1) {
  // code to be executed if condition1 is true
} else if (condition2) {
  // code to be executed if condition2 is true
} else {
  // code to be executed if all conditions are false
}


// example
let age = 10;
if (age < 13) {
  console.log("Person is a child");
} else if (age < 18) {
  console.log("Person is a teenager");
} else {
  console.log("Person is an adult");
}

---

Switch statement

The switch statement is used to select one of many code blocks to be executed. It provides a more efficient way to handle multiple options in your code.

switch (expression) {
  case value1:
    // code to be executed if expression === value1
    break;
  case value2:
    // code to be executed if expression === value2
    break;
  // other cases here
  // ...
  default:
    // code to be executed if expression doesn't match any of the cases
}

Here is an example of computing weekdays and weekend via switch - notice that case's without a break statement simple "fall-through" to the next case:

let day = "Sunday";

switch (day) {
  case "Monday":
  case "Tuesday":
  case "Wednesday":
  case "Thursday":
  case "Friday":
    console.log("Today is weekday");
    break;
  case "Saturday":
  case "Sunday":
    console.log("Today is weekend");
    break;
  default:
    console.log("Invalid day");
}

// prints: "Today is weekend"