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switch-case, ?, truthy/falsy

Let's explore the switch-case statement and the ternary operator for handling conditions without if statements, as well as the concepts of truthy and falsy which determine truthiness in JavaScript.


switch-case Statement​

A switch-case statement is used when you want to compare a specific value with multiple potential values.

Structure of switch-case statement
switch (expression) {
  case value1:
    // Code to be executed if expression matches value1
    break;
  case value2:
    // Code to be executed if expression matches value2
    break;
  // ... (more cases can be added)
  default:
  // Code to be executed if expression doesn't match any case
}

break and default​

break exits the switch-case statement when a condition is satisfied, preventing the evaluation of subsequent conditions.

If break is omitted, even if a condition is satisfied, the subsequent conditions will continue to be evaluated.

default contains the code to be executed when the given expression doesn't match any case.


Example of switch-case statement
const fruit = 'Apple';

switch (fruit) {
  case 'Banana':
    console.log('It\'s a Banana');
    break;
  case 'Apple':
    console.log('It\'s an Apple');
    break;
  case 'Grapes':
    console.log('It\'s Grapes');
    break;
  default:
    console.log('Unknown fruit');
}
// Output: It's an Apple

Conditional Statement Using Ternary Operator​

The ternary operator allows you to write a simple if-else structure more concisely.

Structure of Ternary Operator
condition ? valueIfTrue : valueIfFalse

Example of Ternary Operator
let age = 19;
let result = age >= 20 ? 'Adult' : 'Teenager';

console.log(result); // Output: Teenager

truthy and falsy​

In JavaScript, every value is classified as truthy or falsy.

falsy values are treated as false, while truthy values are treated as true.

This concept is important in determining how values are treated in Boolean (true/false) contexts, which affects the execution of conditional statements.


Below are examples of falsy values.

  • false
  • 0
  • "" (empty string)
  • null
  • undefined
  • NaN

All other values are truthy.

Example of truthy and falsy
let value = 0;

if (value) {
  console.log('It\'s true');
} else {
  console.log('It\'s false');
}

// Output: It's false

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