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Part 10: Working with APIs in JavaScript

  Working with APIs in JavaScript Outline: 1. Introduction to APIs: 1.1 Definition of APIs: Explanation of what an API (Application Programming Interface) is. Understanding the role of APIs in web development. Types of APIs:  RESTful APIs, SOAP APIs, etc. 1.2 Importance of APIs in Web Development: How APIs facilitate communication between different software systems. Use cases of APIs in modern web development. Examples of popular APIs and their impact. 2. Making API Requests: 2.1 HTTP Methods: Overview of common HTTP methods: GET, POST, PUT, DELETE. Explanation of when to use each HTTP method. 2.2 Fetch API: Introduction to the Fetch API in JavaScript. Making simple GET requests with Fetch. Handling responses from Fetch requests. 2.3 Sending Data in API Requests: Using POST requests to send data to the server. Handling different types of data (JSON, form data) in API requests. 3. Handling API Responses: 3.1 Parsing JSON: Importance of JSON (JavaScript Object Notation) in API r...
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Learn JavaScript Step by Step Part 4 Control Flow

Part 4: Control Flow in JavaScript

Welcome to the next part of our JavaScript journey! In this segment, we'll explore control flow in JavaScript. Control flow allows you to make decisions in your code and execute specific blocks of code based on conditions. It's a fundamental concept in programming. At the end of this blog you will get a quiz to test your understanding of this topic. Let's dive in!

Conditional Statements: Making Decisions


Conditional statements are used to make decisions in your code. They allow your program to take different actions depending on whether a certain condition is true or false.

1. If Statement: 

The if statement is the most basic conditional statement. It executes a block of code if a specified condition evaluates to true.
let age = 18;

if (age >= 18) {
    console.log("You are an adult.");
}
If you run the code in VS Code, the output will be:

Output:

You are an adult.

2. Else Statement: 

You can use the else statement along with if to specify a block of code to execute when the condition is false.
let age = 15;

if (age >= 18) {
  console.log("You are an adult.");
} else {
  console.log("You are not yet an adult.");
}
Here, if the age is less than 18, the message "You are not yet an adult" will be displayed.

Output:

You are not yet an adult.

3. Else If Statement: 

The else if statement lets you check multiple conditions sequentially and execute code when one of the conditions is true.
let score = 75;

if (score >= 90) {
  console.log("You got an A.");
} else if (score >= 80) {
  console.log("You got a B.");
} else if (score >= 70) {
  console.log("You got a C.");
} else {
  console.log("You need to improve.");
}
In this example, it checks the score against multiple conditions and assigns a grade based on the score.

Output:

You got a C.

4. Switch Statement:

The switch statement is another way to make decisions based on a specific value. It's particularly useful when you have multiple cases to consider.
let day = "Monday";

switch (day) {
  case "Monday":
    console.log("It's the start of the week.");
    break;
  case "Tuesday":
    console.log("Tuesday vibes!");
    break;
  case "Wednesday":
    console.log("Hump day!");
    break;
  default:
    console.log("It's some other day.");
}

Output:

It's the start of the week.
In this example, the switch statement evaluates the value of day and executes the code block associated with the matching case. The break statement is used to exit the switch block after a case is executed. If none of the cases match, the code block under default is executed.

Loops: Repeating Code

Loops allow you to execute a block of code repeatedly. They are essential for performing tasks that need to be done multiple times.

1. For Loop: 

A for loop is often used when you know how many times you want to repeat an action.
for (let i = 0; i < 5; i++) {
    console.log("Iteration " + i);
  }

Output:

Iteration 0
Iteration 1
Iteration 2
Iteration 3
Iteration 4

2. While Loop:

The while loop repeats a block of code as long as a condition is true.
let count = 0;

while (count < 5) {
    console.log("Count: " + count);
    count++;
}

Output:

Count: 0
Count: 1
Count: 2
Count: 3
Count: 4

3. Do-While Loop:

The do-while loop ensures that the code block runs at least once before checking the condition.
let x = 1;

do {
  console.log("x is: " + x);
  x++;
} while (x <= 3);
In this case, the loop runs once, printing "x is: 1," and then checks the condition. It will run as long as x is less than or equal to 3.

Output:

x is: 1
x is: 2
x is: 3
Now lets change x value as 5 and run the code again. You will still get the ouput but only as x=5. It means the code always runs even the condition is not true.
let x = 5;

do {
    console.log("x is: " + x);
    x++;
} while (x <= 3);

Output:

x is: 5
Control flow, including conditional statements, switch statement and loops, is a powerful way to control the flow of your JavaScript programs. It enables your code to make decisions and execute tasks repeatedly, making your applications more dynamic and responsive. In the next part, we'll delve into functions, a key concept in JavaScript for organizing and reusing code. Stay tuned and keep coding!
Now let's test your knowledge of control flow in JavaScript. Here's a quiz of 10 multiple-choice questions.

JavaScript Control Flow Quiz

1. Which keyword is used to declare variables with block scope in modern JavaScript?
a) var
b) let
c) const
d) int
Show Answer

Ans: b) let
Explanation: let in JavaScript provides improved scoping, avoids hoisting-related problems, allows for reassignment, supports block-level declarations, and helps catch errors through the temporal dead zone. It's a recommended choice for variable declarations in modern JavaScript development.


2. What is the purpose of a conditional statement in JavaScript?
a) To repeat code multiple times
b) To execute code when a condition is met
c) To declare variables
d) To define functions
Show Answer

Ans: b) To execute code when a condition is met
Explanation: The purpose of a conditional statement in JavaScript is to control the flow of your code based on certain conditions or criteria. Conditional statements allow you to make decisions within your program, executing different code blocks depending on whether a specific condition evaluates to true or false. They are fundamental for building dynamic and responsive programs.


3. In the following code snippet, what will be printed to the console?
let temperature = 28;

if (temperature > 30) {
  console.log("It's hot outside!");
} else {
  console.log("It's not too hot.");
}
a) It's hot outside!
b) It's not too hot.
c) The code will result in an error.
d) Nothing will be printed.
Show Answer

Ans: b) It's not too hot.
Explanation: when you run this code, it will print "It's not too hot." to the console because the temperature is not greater than 30, and the code inside the else block is executed.


4. What is the purpose of the break statement in a switch statement?
a) To terminate the program
b) To skip the current case and continue with the next one
c) To exit the switch statement
d) To print a message to the console
Show Answer

Ans: c) To exit the switch statement
Explanation: The break statement in a switch statement serves a crucial role in controlling the flow of execution within the switch block. Its primary purpose is to exit the switch block once a specific case is matched and executed.


5. In a switch statement, which keyword is used to specify a default case?
a) default
b) case
c) else
d) otherwise
Show Answer

Ans: a) default

Explanation: the default keyword in a switch statement is a best practice for handling cases that are not explicitly covered by other case conditions. It adds predictability, readability, and error prevention to your code, making it a valuable component of control flow in JavaScript.

6. What will be the output of the following switch statement?
let day = "Wednesday";

switch (day) {
  case "Monday":
    console.log("It's the start of the week.");
    break;
  case "Wednesday":
    console.log("Hump day!");
    break;
  default:
    console.log("It's some other day.");
}
a) It's the start of the week.
b) Hump day!
c) It's some other day.
d) Nothing will be printed.
Show Answer

Ans: b) Hump day!
Explanation: The "Hump day!" message is printed to the console because the case label "Wednesday" matches the value of the day variable, and the associated code block is executed. The break statement ensures that no other case labels or the default case are evaluated after the matching case is found and executed.


7. In a for loop, which part of the loop controls how many times it will execute?
a) Initialization
b) Condition
c) Iteration
d) Block of code
Show Answer
Ans: b) Condition
Explanation: In a for loop in JavaScript, the part of the loop that controls how many times it will execute is the condition. The condition is the second component of the for loop syntax and is enclosed within the parentheses following the for keyword.
Here's the basic structure of a for loop:
for (initialization; condition; iteration) {
    // Code to be executed
  }
Initialization: This is typically where you initialize a loop control variable, which is used to keep track of the loop's progress. It's executed once before the loop starts.
Condition: The condition is a boolean expression that determines whether the loop should continue executing or terminate. If the condition evaluates to true, the loop continues; if it evaluates to false, the loop exits.
Iteration: The iteration part is where you update the loop control variable after each iteration of the loop. It is executed at the end of each loop iteration.
The loop continues to execute as long as the condition remains true. When the condition becomes false, the loop terminates.
For example, in the following for loop:
for (let i = 0; i < 5; i++) {
    // Code to be executed
}
The condition i < 10 controls how many times the loop will execute. The loop will run as long as i is less than 10. Once i becomes equal to or greater than 10, the condition becomes false, and the loop stops executing. In this case, the loop runs 10 times because it iterates from i = 0 to i = 9.
8. Which type of loop is best suited when you don't know in advance how many times you need to repeat a block of code?
a) for loop
b) while loop
c) do-while loop
d) switch loop
Show Answer
Ans: b) while loop
Explanation: When you don't know in advance how many times you need to repeat a block of code, a while loop is the best-suited loop type in JavaScript. The while loop is designed for situations where the loop's continuation depends on a condition, and that condition may not be known initially or may change during the loop's execution.

9. In a do-while loop, the code block will always execute:
a) Once, regardless of the condition
b) As long as the condition is true
c) Only when the condition is false
d) It depends on the iteration count
Show Answer
Ans: a) Once, regardless of the condition
Explanation: The key feature of a do-while loop is that the code block is guaranteed to execute at least once, regardless of the condition. For example, you might use a do-while loop when you want to ask the user for input at least once and then continue asking based on their response:
let userInput;

do {
  userInput = prompt("Enter 'exit' to quit:");
} while (userInput !== "exit");
In this case, the code block inside the do will run at least once to prompt the user for input, and then it will continue to execute as long as the user doesn't enter "exit."

10. Which of the following is not a valid JavaScript variable declaration keyword for block-scoped variables?
a) var
b) let
c) const
d) int
Show Answer
Ans: d) int
Explanation: int is not a valid variable declaration keyword in JavaScript. It is not recognized by the JavaScript language, and attempting to use it to declare variables will result in a syntax error.



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