TLDR;
This session covers JavaScript functions, starting with basic function declarations and progressing to more advanced concepts like parameterized functions, rest parameters, return type functions, arrow functions, and callback functions. The session also touches on asynchronous behavior in JavaScript and how to handle it using callbacks.
- Basic and Parameterized Functions
- Rest Parameters
- Return Type Functions
- Arrow Functions
- Callbacks and Asynchronous JavaScript
Introduction to Functions [45:58]
The session begins with an introduction to functions in programming, defining a function as a block of code that performs a specific task. Functions are similar to procedures, taking inputs and returning outputs with a clear relationship between them. The trainer explains that functions help in executing sets of instructions without writing extra lines of code.
Setting Up the Development Environment [49:21]
To run JavaScript code, the trainer uses VS Code, recommending the creation of a dedicated folder for each project to maintain organization. The session demonstrates how to open a folder in VS Code using the command prompt and the code . command. It also covers creating index.html and index.js files, generating boilerplate code in the HTML file using the ! shortcut, and linking the JavaScript file to the HTML file using the <script src> tag.
Basic Function Declaration [1:03:03]
The trainer explains the structure of a basic function, which includes the function keyword, a function name, parentheses, and curly braces containing the statements to be executed. The importance of functions in reusing code is highlighted, contrasting it with the inefficiency of duplicating code. The trainer demonstrates how to declare and call a simple function that prints "Good Morning" to the console.
Parameterized Functions [1:19:15]
The session introduces parameterized functions, which accept parameters (data) inside the function. The trainer explains that parameters are placeholders for arguments, which are the actual data passed during the function call. A function add is created to demonstrate how to pass two parameters, a and b, and how to use these parameters to perform addition. The difference between parameters and arguments is clarified, with arguments being the actual data and parameters being references to those arguments.
Rest Parameters [1:37:14]
Rest parameters are introduced as a way to pass an indefinite number of arguments to a function as an array. The trainer uses the example of a supermarket cart to illustrate how rest parameters can be used to handle an unknown number of items. The syntax for rest parameters involves using three dots (...) before the parameter name. It's emphasized that the rest parameter must be the last parameter in the function definition. The session demonstrates how to use rest parameters to create a function that accepts any number of fruits and prints them.
Return Type Functions [2:00:53]
The session covers return type functions, which return a value (either primitive or non-primitive) after execution. The trainer revisits the add function, modifying it to return the sum of a and b instead of directly printing it. The importance of using the console.log statement to print the returned value is emphasized. It's also noted that the return keyword should be the last statement inside the function.
Arrow Functions [2:04:16]
Arrow functions, a feature of ES6 (ECMAScript version 6), are presented as a shorthand syntax for writing functions. The trainer explains that arrow functions provide a more concise way to declare functions, often used for simple tasks like callbacks. The basic syntax of an arrow function is () => {}. The session demonstrates how to declare an arrow function and store it in a variable, creating a function expression. It's shown that if an arrow function has a single statement, the curly braces can be omitted.
Callback Functions and Asynchronous JavaScript [2:16:19]
The session introduces callback functions and their role in handling asynchronous behavior in JavaScript. JavaScript is described as an asynchronous language, meaning it doesn't wait for each line of code to finish executing before moving on to the next. The setTimeout function is used to demonstrate asynchronous behavior, showing how it delays the execution of a function. Callback functions are defined as functions passed as arguments to other functions. The trainer explains how callbacks can be used to ensure that certain functions are executed only after others have completed, thus managing the asynchronous nature of JavaScript.