Conditional Statement

Importance of Conditional Statements in Computer Programming

• Decision making: Without conditional statements, a program would follow a linear sequence of commands, regardless of the input or state of the system. Conditional statements make it possible for programs to make decisions and respond appropriately to different situations.
• Flow control: Conditional statements, in combination with loops and other control structures, allow the easy manipulation of a program's control flow, enabling it to follow a specific series of commands based on a wide range of factors and inputs.
• Error handling: Conditional statements allow programs to check for erroneous input or unexpected conditions and can help prevent your program from crashing or producing incorrect results due to an unhandled exception.
• Code reusability and modularity: By using conditional statements, you can create reusable, modular code that can be applied in different scenarios and contexts, potentially reducing the amount of redundant code and making it easier to maintain and update.

Types of Conditional Statements

There are various types of conditional statements in computer programming.

If Statements

if course == "Computer Science":
    print("You are studying Computer Science")

if (condition) {
  // Code block to be executed
}

if (condition) {
    // Code block to be executed
}

if condition:
    # Code block to be executed

If-Else Statements

if score >= 50:
    print("You passed!")
else:
    print("You failed!")

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

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

if condition:
    # Code block to be executed if condition is true
else:
    # Code block to be executed if condition is false

Switch-Case Statements

switch (grade) {
  case 'A':
    System.out.println("Excellent!");
    break;
  case 'B':
    System.out.println("Good!");
    break;
  case 'C':
    System.out.println("Average!");
    break;
  default:
    System.out.println("Unknown grade");
}

switch (variable) {
  case value1:
    // Code block to be executed if variable equals value1
    break;
  case value2:
    // Code block to be executed if variable equals value2
    break;
  // ...
  default:
    // Code block to be executed if none of the cases match
}

switch (variable) {
  case value1:
    // Code block to be executed if variable equals value1
    break;
  case value2:
    // Code block to be executed if variable equals value2
    break;
  // ...
  default:
    // Code block to be executed if none of the cases match
}

Basic Python Conditional Statements

• If Statement: The fundamental conditional statement, which comprises an "if" keyword, a condition (expression), and a colon, followed by an indented code block.
• If-Else Statement: An extension of the "if" statement that includes an "else" keyword, a colon, and an indented block of code to be executed when the "if" condition is not met (i.e., false).
• If-Elif-Else Statement: A more complex structure that accommodates multiple conditions that need to be checked in a sequence. It consists of the "if" statement, followed by one or multiple "elif" (short for "else if") statements, and an optional "else" statement at the end.

if condition1:
    # Code block to be executed if condition1 is true
elif condition2:
    # Code block to be executed if condition1 is false and condition2 is true
else:
    # Code block to be executed if both condition1 and condition2 are false

Python Conditional Statement Examples

# Example 1: Simple If Statement
age = 18
if age >= 18:
    print("You are eligible to vote.")

# Example 2: If-Else Statement
temperature = 35
if temperature >= 30:
    print("It's hot outside.")
else:
    print("It's not hot outside.")

# Example 3: If-Elif-Else Statement
grade = 75
if grade >= 90:
    print("A")
elif grade >= 80:
    print("B")
elif grade >= 70:
    print("C")
elif grade >= 60:
    print("D")
else:
    print("F")
  

Python If-Elif-Else Statement

if condition1:
    # Code block to be executed if condition1 is true
elif condition2:
    # Code block to be executed if condition1 is false and condition2 is true
elif condition3:
    # Code block to be executed if condition1 and condition2 are both false, and condition3 is true
else:
    # Code block to be executed if all conditions are false

age = 25

if age < 13:
    print("Child")
elif age < 18:
    print("Teenager")
elif age < 30:
    print("Young adult")
elif age < 60:
    print("Adult")
else:
    print("Senior")

JavaScript Conditional Statements

• If Statement: It comprises the "if" keyword followed by a condition enclosed in parentheses and a code block enclosed within curly braces.
• If-Else Statement: This statement extends the "if" statement with an "else" keyword followed by a code block enclosed within curly braces. The "else" block is executed if the "if" condition evaluates to false.
• Switch-Case Statement: It allows the evaluation of an expression and execution of different code blocks depending on the expression's value. The Switch-Case statement consists of the "switch" keyword, the expression enclosed in parentheses, and a set of cases enclosed within curly braces.

// If Statement
if (condition) {
  // Code block to be executed if condition is true
}

// If-Else Statement
if (condition) {
  // Code block to be executed if condition is true
} else {
  // Code block to be executed if condition is false
}

// Switch-Case Statement
switch (expression) {
  case value1:
    // Code block to be executed if expression equals value1
    break;
  case value2:
    // Code block to be executed if expression equals value2
    break;
  //...
  default:
    // Code block to be executed if none of the cases match
}

JavaScript Conditional Statement Examples

// Example 1: Simple If Statement
let age = 18;
if (age >= 18) {
  console.log("You are eligible to vote.");
}

// Example 2: If-Else Statement
let temperature = 35;
if (temperature >= 30) {
  console.log("It's hot outside.");
} else {
  console.log("It's not hot outside.");
}

// Example 3: Switch-Case Statement
let grade = 'B';
switch (grade) {
  case 'A':
    console.log("Excellent!");
    break;
  case 'B':
    console.log("Good!");
    break;
  case 'C':
    console.log("Average!");
    break;
  default:
    console.log("Unknown grade");
}
  

JavaScript Ternary Operator

variable = condition ? value_if_true : value_if_false;

let temperature = 25;
let isHot = temperature >= 30 ? "Yes" : "No";
console.log("Is it hot outside? " + isHot);

Common Uses and Examples of Conditional Statements

Conditional Statement Examples in Real-Life Programming

• Form Validation: Conditional statements are often used to validate user input in registration forms, login forms, or any data-entry form. For example, they can be utilized to check if required fields are filled in, passwords meet specific criteria, or email addresses follow a specific format.
• Dynamic Web Content: In web development, conditional statements can be employed to display custom content or visual elements on the web page depending on user preferences, device properties, or other variable factors. A common example is adjusting the content and layout of a webpage based on whether it is viewed on a desktop or mobile device.
• Access Control: Conditional statements are used in the implementation of access control mechanisms, such as checking if a user is logged in or has the required permissions to access certain content or features of an application.
• Error Handling: In software development, conditional statements play a significant role in error handling. They enable the program to check for possible errors, such as invalid input or unexpected conditions, and respond appropriately - either by displaying an error message, logging the error for review, or safely handling the exception.
• Game Development: In video game development, conditional statements are utilized to maintain game rules, trigger events, and control character behaviour or user interaction, depending on the game state or environment variables.

Best Practices when Using Conditional Statements

• Keep conditions simple: Avoid using overly complex conditions that are hard to understand or maintain. If required, break down complex conditions into smaller, simpler expressions or use intermediate variables.
• Use meaningful variable and function names: When constructing conditions, using clear and descriptive variable and function names can make your code more accessible and easier to understand for others working on or reviewing the code.
• Prefer early returns or guard clauses: Instead of nesting multiple if statements, consider using early returns or guard clauses, which can make your code more readable and less prone to errors. This is particularly useful when testing for error conditions or validating input.
• Limit the depth of nested conditional statements: Deeply nested conditional statements can make your code harder to read and maintain. Aim to limit the depth of nesting, and if possible, refactor your code by extracting nested blocks into separate functions.
• Avoid excessive use of ternary operators: While ternary operators offer a more compact and elegant way to represent simple if-else statements, overusing them can make your code difficult to understand and maintain.
• Consistent indentation and code formatting: Using consistent indentation and code formatting practices can help improve the readability of your code, making it easier to identify the structure and flow of your conditional statements.