JavaScript Question
Tags: webdev, javascript, beginners, programming
Published: 2024-02-02 13:31:22

**Q1 What is JavaScript:**

- JavaScript is used to create client-side dynamic pages.
- JavaScript is object-based scripting language which is lightweight and cross-platform. 
- JavaScript is an object-based scripting language, meaning it uses objects to represent data and functionality, rather than using simple variables and functions. This makes it easier to write and manage complex applications.
- JavaScript is considered lightweight because it is easy to learn and its syntax is simple, which means it is well-suited for small to medium-sized web applications.
-  It is also cross-platform, which means it can be run on any device that has a web browser, making it a popular choice for web development.**js is not compiled language .**

A programming language is a type of computer language that consists of a set of instructions for communicating with computers. 

A scripting language is a kind of programming language that is used to automate the execution of operations in a runtime environment.

A script or scripting language is a computer language that does not need
 the compilation step and is rather interpreted one by one at runtime.

the programming languages that are compiled first before running, scripting languages do not compile the file and execute the file without being compiled.

Scripting languages are used on the server-side as well as the client-side and are also widely used in web applications. The languages like JavaScript, Python, PHP, and Perl are examples of server-side scripting languages, and JavaScript, jQuery, AJAX are examples of client-side scripting languages.

**What is meant by interpreted programming language?**
An interpreted language is a programming language whose implementations execute instructions directly and freely, 
without previously compiling a program into machine-language
instructions.

**What is a Typed language?**
Typed Language is in which the values are associated with values and not with variables. It is of two types:
**Dynamically:** in this, the variable can hold multiple types; like in JavaScript, a variable can take number, chars ,object.
**Statically:** in this, the variable can hold only one type, like in Java a variable declared of string can take only set of characters and nothing else.

JavaScript follow synchronous pattern

JavaScript code is a single thread, which means that code can only do one task at a time.

A single-threaded process is the execution of programmed instructions in a single sequence.

**. Dynamic Typing**
JavaScript supports dynamic typing which means types of the variable are defined based on the stored value. For example, if we declare a variable x then we can store either a string or a Number type value or an array or an object. This is known as dynamic typing.

**Is JavaScript a case-sensitive language?**
Yes, JavaScript is a case sensitive language.  The language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.

Since JavaScript is a loosely(dynamically) typed language, variables in JS are not associated with any type. A variable can hold the value of any data type.
For example, a variable which is assigned a number type can be converted to a string type:
var a = 23;
var a = "Hello World!";

**2) Advantages:/feature.**

All popular web browser support JavaScript as they provided built in execution environment.
js follow the syntax and structure of the c programming language. Thus it is a structured programming language  
JavaScript is a lightweight scripting language because it is made for data handling at the browser only.
Server interaction is less
Feedback to the visitors is immediate
Interactivity is high
Interfaces are rich
Speed. Client-side JavaScript is very fast because it can be run immediately 
within the client-side browser.
	The biggest advantage of JavaScript having a ability 
to support all modern browsers and produce an equivalent result
Display date and time 
Dynamic drop down menus.


3) Disadvantage:
No support for multithreading
No support for multiprocessing
Reading and writing of files is not allowed


**What is the difference between null & undefined?**
Undefined means a variable has been declared but has not yet been assigned a value. On the other hand,
 null is an assignment value. It can be assigned to a variable as a representation of no value. Also, undefined and null are two distinct types: undefined is a type itself (undefined) while null is an object.

Storing a value in a variable is called variable initialization.

**What are undeclared and undefined variables?**

Undeclared variables are those that do not exist in a program and are not declared. If the program tries to read the value of an undeclared variable, then a runtime error is encountered.

Undefined variables are those that are declared in the program but have not been given any value. If the program tries to read the value of an undefined variable, an undefined value is returned.


Types of functions: Named and Anonymous function in JavaScript???
In JavaScript, there are two types of functions: named functions and anonymous functions.
A named function is a function that has a name. It can be defined using the function keyword followed by the function name, a set of parentheses, and a set of curly braces that enclose the function's body.
```JavaScript
Here's an example of a named function:

function addNumbers(a, b) {
  return a + b;
}
```
An anonymous function is a function that does not have a name. It can be defined using the function keyword, followed by a set of parentheses and a set of curly braces that enclose the function's body, without any function name. Anonymous functions are often used as callback functions, as function arguments or in immediately invoked function expressions (IIFE).
```JavaScript
Here's an example of an anonymous function:

let sum = function(a, b) {
  return a + b;
} 
```
Note that in the example above, the function is assigned to a variable (sum), so it can be invoked later by calling that variable as a function. Anonymous functions can also be immediately invoked by enclosing the function definition in parentheses followed by an additional set of parentheses:

```JavaScript

(function() {
  console.log("This is an immediately invoked anonymous function.");
})();
```

in this case, the function is defined and invoked immediately without being assigned to a variable.
Interactivity is high in JavaScript .. explain in simple

ChatGPT
In simple terms, "interactivity" refers to how much a user can interact with a web page or application. JavaScript is a programming language that is commonly used in web development to add interactivity to websites.
With JavaScript, we can create interactive features such as drop-down menus, pop-up windows, sliders, animations, and more. These features can respond to user actions such as clicks, mouse movements, or keyboard inputs, allowing users to interact with the website and its content in meaningful ways.
For example, with JavaScript, a user can click a button to show or hide content on a web page, or drag and drop items to rearrange them. JavaScript can also be used to validate form inputs, perform calculations, and even create interactive games.
Overall, JavaScript's ability to add interactivity to web pages is a key reason why it is such a popular programming language for web development.
**JavaScript is a programming language .explain** 
ChatGPT
Yes, JavaScript is a programming language that is used primarily for web development, but can also be used for other purposes such as server-side programming, desktop applications, and mobile app development.

One of the main uses of JavaScript is to create dynamic and interactive websites. JavaScript can be used to manipulate the content and styling of a web page, add interactivity through event handling, and communicate with web servers to update content without requiring a full page refresh.
Overall, JavaScript is a versatile programming language that is widely used for a variety of applications, and its popularity and importance in web development continues to grow.