JavaScript definition

JavaScript (JS) is a prototype base, high level, interpreted, multi-paradigm, single-threaded dynamic. To break all this down, JavaScript being prototype base means it allows machine of object without first defining its classes. It has lots of abstraction so you don't have to deal with memory management and co as a high-level language, by interpreted language it means it runs without compilation and can be written as either an object oriented or functional programming as a multi paradigm language. JavaScript also runs only one line of code at any given time as a single threaded language and finally, as a dynamic language; the interpreter assigns a type of variable at runtime based on the variable value at that time

uses of JavaScript

Developers use JavaScript to build complex interactive websites and browser games, and to connect servers to websites and web applications. Because of this versatility, it's easy to see why this language is the most commonly used programming language in the world, so basically we can use JS for; Web development, Web applications, Mobile applications, Game, Presentation, Server applications, Web servers e.t.c .

History of JavaScript

JavaScript was invented by Brendan Eich in 1995. It was developed for Netscape 2, and became the ECMA-262 standard in 1997. After Netscape handed JavaScript over to ECMA, the Mozilla foundation continued to develop JavaScript for Firefox browser. Mozilla's latest version was 1.8

Fundamentals of JavaScript

In order to know and use JavaScript, you need to master its syntax. This fundamentals comprises of; variables, datatypes, operators, flow control, loops and functions

variables

In every programming language, variables are used to store data(values) temporally in the computer's memory, it is also a pointer to a data stored in the computer's memory. There are three keywords for declaring variables in JavaScript; the var, let and const keywords

Difference between var, let and const

Let and const keywords came the new edition of JavaScript, so var was already there. Speaking about their difference; var variables are function-scoped, while let and const variables are block-scoped. Also, a const variable can't be redeclared

sample code

Var variable1="hello world";

Let variable2="hello world";

Const variable3="hello world";

Console.log(variable1, variable2, variable3)

Output: hello world hello world hello world

Note: console.log(...) Is used for outputting our code result and every line of code should end with a semicolon (;).

We have what is called concatenation in JS, it's for outputting a massage and various variable at once using the plus sign(+) Example:

Const name = "John";

Const age =34;

Console.log("my name is "+name+", and I am"+age+" years old")

There is also what is called commenting in JS, when you comment, it means the interpreter will skip the code. We have single line and multiple line comments, the double forward slashes(//) is for single line while the forward slash and asterisk (/..../) is multiple line. This also help in code readability

datatypes

Datatypes determines the type of data to held by our variables, it is a classification of data which tells the interpreter how the programmer Intends to use the data. We have the primitive and none primitive datatypes

primitive datatypes

In JS, a primitive (primitive value and datatypes) is data that is not an object and has no methods or properties. We have the following under the primitive datatypes;

string

A string is a sequence of one or more characters that may consist of letters, numbers, or symbols

code sample

Let name = "ifedili";

Note: string values are written with double quotes ("")

number datatype

This is made of both integers and floating point numbers, it stores numbers in particular

Code sample

Let numbers= 12345;

boolean

In JavaScript, a boolean holds a value that can either be TRUE or FALSE. If you need to know "yes" or "no" about something, then you would want to use the boolean function

code sample

Let answer= true;

undefined

This deals with empty values, a variable that has not been assigned a value is of type undefined. A function also returns undefined if a value was not returned.

code sample :

Let emptyvalue=

Or

Let emptyvalue=undefined

non-primitive datatypes

Non-primitive datatypes are also called reference datatypes or object references as they reference a memory location where data is stored. This consist of arrays and objects e.t.c

Arrays

An array is an object that can store multiple values of the same datatype at once

Code sample:

Const words= ["hello", "world", "welcome"];

Note:. Use the square brackets ([]) to list your arry value. The above array is an array of string, do we equally have array of other datatypes

Objects

An object is a standalone entity, with properties and type . We use objects to hold a group of data(key as the variable and value)

Code sample: Const person={ name: "John" age: 34 istall: true address:( Street: no 4 genesys city: Enugu ) }

//To output the values of keys

console.log(pesorn["name"])

//To get the value of a sub object

console.log(person["address"]["city"]) //or

console.log(person_address.city) We can have sub object in an object such as address in the above code.

operators

Operators is a special symbol used to perform operation on operands (values and variable)

arithmetic operators

This operators are used for performing arithmetic operation like addition and subtraction:

Addition; +

Subtraction; -

Multiplication; *

Division; /

Modules; %

Exponential; **

Code sample:

Console.log(1+23*4/5)

comparison operators

Greater than;>

Less than; <

Greater than or equal to; >=

Less than or equal to; <=

Equal to; ==

Not equal to; !=

Code sample:

console.log(2<3, 4==5)

logical operators

Not; !

And; &&

Or; ||

Null coalescing; ??

Code sample:

console.log(1>2 && 3=20)

flow control

This is a way to control the flow of codes and telling the program to do this if a particular condition is true/false. To do this, we use the following functions:

if else conditional statement

The if else conditional statement takes in conditions to control our code.

Code sample: Let i=0 If(ii//condition){ console.log("hello") }else{ console.log("no compliment")//this will run If non of the condition is true }

Note: the else serves as default if none of the conditions are true

Switch

This different from if else, this takes a parameter and compares the parameter with each case (it's made up of cases)

Code sample:

Const dayoftheweek=4; Switch (dayoftheweek){ Case 1: console.log (week day); break; default: console.log(weekend);

Note: the default will run if none of the cases are true.

loops

In every programming language, loops are used to print a cidr multiple times, there are three stages in a loop; the initialization, condition and increment/decrement

for loop

This is most common loop in programming language, like I said earlier it comprises of initialization, condition and increment/decrement.

Code sample:

For(let i=0//initialization;i<3//condition;I++//increment/decrement){ Code to multiply }

while loop

The while loop serves the same function as the for loop but has segments

Code sample: Let i=0

While (I<3//condition){ console.log("hi")//code multiply }

Note: code to run follows the condition and this will determine how many times the code will appear.

We have other loops but this is the basic ones.

function

This is last we are going to be treating, it is a block of code that takes in an input and returns an output. A function in js is noted by the function keyword followed by brackets where our parameters (variables to be used in our function) will be and a braces where our code will be Code sample:

Function add (x, y){ return x+y }

Note: "add" is our function variable name and we are to return a value using the keyword "return".

Arrow function

This is just like a shortcut for writing function in js it's called the arrow function because it comes with "=>" and doesn't have the function keyword.

Code sample:

const add (x,y)=>{return x+ y} console.log(add)

conclusion

This are the fundamentals of JavaScript with this you can get started with JS. JavaScript comprises of a lot, you need to go further in order to master JavaScript very well.