Getting Started with JavaScript - 1

What is JavaScript?

Javascript is well known as the programming language for the Web. It's a client-side scripting language.

What is its function?

Basically, javascript functions when some action is performed by the client. The actions can be hovering over using a mouse, clicking on something, scrolling, anything based on what's coded.

Syntax?

<script type = “text/javascript”> 
// Enter the code here.
</script>

   // Linking an external javascript file.
  <script src="example.js"></script>

Now let's dive into Javascript basics.

- Comments

// Single line comments are typed here
/* Multi line comments are typed in this. 
    Comments are used to explain the code, 
    Basically, to make the code understandable to the reader.*/

- Variables

These hold values and are used to perform different operations.

3 Types:

1) var - Frequently used. Values can be assigned can be modified over the operations and working. Works only in the functions its declared in.

var example = "value";

2) const - These values can't be modified again and again. The values assigned in the start remains unchanged until the end.

const example = "value";

3) let - Values assigned can change, works only inside the particular block.

let example = "value";

- Datatypes

Datatype	Example	Syntax
Number	300.3	var roll_no = 10;
Null	null	var example = null;
Undefined	undefined	var example; typeof example;
String	"Hello"	var text = "Hello";
Boolean	True/False	var answer = false;
Symbol	Giovanni Rovelli	var example = /()/;

- Objects

It's another type of data-type which stores in key-value pair format.

var student = {
// Here, name,roll,dob are the keys. 
// Opposite to them are their respective values.
  name : Bhumi Khokhani,
  roll : 10,
  dob : "2000-03-27",
  age : function() {
  // Code written for the function
  }; //Method
}

- Functions

Set of code written to perform a specific task. It runs when it's called. Having functions also increases the reusability of code.

Two steps to create as function:

1) Define it

2) Call it

//Defining the function.
function function_name ( parameters ) {
//Block of Code
var abc=parameters;
return abc; //returns this value at the end of the function. It's optional.
}
function_name(parameters); //Calling the function.

- Arrays

A group of similar datatypes is called an array. We can access by referring to the index number.

Syntax

// First way of defining an array
datatype array_name=["value1", "value2", "value3", ...];
//Second way of defining an array
datatype array_name = [];
array_name[0] = "value1";
array_name[1] = "value2";
array_name[2] = "value3";
//Third way of defining an array
datatype array_name = new Array("value1", "value2", "value3");
// Accessing the array elements
datatype variable_name = array_name[index_value];
// Altering a value of array
array_name[index_value] ="new value";
// Printing the array elements
for (var i = 0; i < array_name.length; i++) {
     console.log(array_name[i]);
}

Functions on Array

Function	Definition	Example
concat()	Used for concatenating arrays.	array_name.concat(arr1, arr2);
join()	Joining all elements in the particular array giving back a string.	array_name.join("*");
indexof()	Returns the first position (index) of an array.	array_name.indexof();
lastindexof()	Returns the last position (index) of an array.	array_name.lastindexof();
sort()	Sorting of array elements in alphabetical order.	array_name.sort();
reverse()	Sorting of array elements in reverse alphabetical order.	array_name.reverse();
shift()	Popping of first element, and returning the value of the popped element.	array_name.shift();
unshift()	Pushing of element in the beginning of the array.	array_name.unshift("value");
splice()	Used for adding items to te array, it returns the deleted items of the array. // pushing index; no_of items to be deleted; item value	array_name.splice(index1, no._of "values");
slice()	Derives a new array form the existing array. Slicing doesn't affect the already existing array. // index1 slicing begins, index2 slicing end.	array_name.slice(index1, index2);
toString()	Converts the array separated by commas to a single string.	array_name.toString();
push()	Pushing an item to the end of the array.	array_name.push(item);
pop()	Popping an item from the end of the array.	array_name.pop();

- Operators

1) Basic Operators

Operator	Definition	Example
+	Addition.	var1 = var2 + var3;
-	Subtraction.	var1 = var2 - var3;
*	Multiplication.	var1 = var2 * var3;
/	Division.	var1 = var2 / var3;
%	Modulus.	var1 = var2 % var3;
++	Increment.	var1 ++;
--	Decrement.	var1 --;

2) Bitwise Operator

Operator	Definition	Example
&	AND	var1 & var2
|	OR	var1 | var2
~	NOT.	~ var1
^	XOR	var1 ^ var2
<<	Left Shift	var1 << var2
>>	Right Shift	var1>>var2

3) Comparison Operator

Operator	Definition	Example
==	Equals to	var1 == var2
===	Equal to or type	var1 === var2
!=	Not equal to	var1 != var2
!==	Not equal to or type	var1 !== var2
<	Less than	var1 < var2
>	Greater than	var1>var2
?	Ternary Operator	var1 ? var2
<=	Less than or equal to	var1<=var2
>=	Greater than or equal to	var1>=var2

4) Logical Operators

Operator	Definition	Example
&&	Logical AND	var1 && var2
||	Logical OR	var1 || var2
!	Logical NOT	!(var1 == var2)

Yet, Javascript consists of many different attributes, functions, methods etc., which I will cover in the next blog.

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Wrapping Up

Hope this article gave you some basic knowledge on Javascript and it's working. Feel free to put up any questions if you have/had. I will try my best to answer them.

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