JavaScript as a Programming Language: History and Evolution

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software is nothing more than data plus instructions.

What is the programming language?

Programming language is just a tool that allows us to write code that will instruct a computer to do something.

What is the JavaScript?

JavaScript is a high level language, which means that we don’t have to think about a lot of complex stuff such managing computer’s memory while it runs the program.

There are a lot of so-called abstractions over all these small details that we don’t want worry about. And this makes the language a lot easier to write and to learn.

It’s Object Oriented(Based on objects for storing most kind of data) and multi-paradigm(Can use different programming styles) language.

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JavaScript is case-sensitive

Popularity of JavaScript

Dynamic Typing

JavaScript has a feature called dynamic typing. It means when you create a new variable, you don’t have to manually define the data type of the value that it contains.

JavaScript automatically determines the data type of the value when it’s stored into a variable. In JavaScript that value has a type not variable.

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It’s simply mean that we can easily change the type of a value that is hold by a variable.

Programming Paradigms in JavaScript

JavaScript supports both imperative and declarative programming styles:

Imperative Programming : Focuses on how to perform tasks by controlling the flow of computation. This includes approaches like procedural and object-oriented programming, often using constructs like async/await to handle asynchronous actions.
Declarative Programming : Focuses on what should be done rather than how it’s done. It emphasizes describing the desired result, such as with arrow functions, without detailing the steps to achieve it.

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variable, data types, conditionals, loops, functions, and objects are the LEGO of any programming language.

Variables

Variable can be said as container / label to contain some value. To store some value in memory, the variable is used for it.

Variables can be declared using var, let, or const
JavaScript is dynamically typed, so types of values are decided at runtime.
You don’t need to specify a data type when creating a variable.
var (function and global scoped), let and const (local scoped).
var can be re-declared in the same scope, but let and const cannot be re-declared.

var x = 10;
var x = 20; // Allowed

let y = 30;
let y = 40; // SyntaxError

const z = 50;
const z = 60; // SyntaxError

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We can change the elements of array or objects even if declared as const. How? Because their reference is saved in stack while value in heap.

let name = "JS";

Rules for Naming Variables

When naming variables in JavaScript, follow these rules

Variable names must begin with a letter (A to Z or a to z), underscore (_), or dollar sign ($).
Subsequent (after that) characters can be letters, numbers, underscores, or dollar signs.
Variable names are case-sensitive (e.g., age and Age are different variables).
Reserved keywords (like function, class, return, etc.) cannot be used as variable names.

Data Types

It’s an attribute (quality) that identifies (recognizes) a piece of data and instructs (tells) a computer system on how to interpret (explain) its value is called a data type.

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Each data type has its own methods and operations that control how it can be used.

The data has type (e.g. number, string

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