Table of Content

JavaScript Variables

A JavaScript variable is the simple name of the storage location where data is stored. There are two types of variables in JavaScript which are listed below: 

• Local variables: Declare a variable inside of a block or function.
• Global variables: Declare a variable outside function or with a window object.

Example: This example shows the use of Javascript variables.

Output: 

Apple
45

JavaScript Operators

JavaScript operators are symbols that are used to compute the value or in other words, we can perform operations on operands. Arithmetic operators ( +, -, *, / ) are used to compute the value, and Assignment operators ( =, +=, %= ) are used to assign the values to variables.

Example: This example shows the use of javascript operators.

Output: 

26

JavaScript Expression

Expression is the combination of values, operators, and variables. It is used to compute the values.

Example: This example shows a JavaScript expression.

Output:

10
50

JavaScript Keyword

The keywords are the reserved words that have special meanings in JavaScript. 

// let is the keyword used to
// define the variable
let a, b;
// function is the keyword which tells
// the browser to create a function
function GFG(){};

JavaScript Comments

The comments are ignored by the JavaScript compiler. It increases the readability of code. It adds suggestions, Information, and warning of code. Anything written after double slashes // (single-line comment) or between /* and */ (multi-line comment) is treated as a comment and ignored by the JavaScript compiler.

Example: This example shows the use of javascript comments.

Output:

50

JavaScript Data Types

JavaScript provides different datatypes to hold different values on variables. JavaScript is a dynamic programming language, which means do not need to specify the type of variable. There are two types of data types in JavaScript. 

• Primitive data type
• Non-primitive (reference) data type

// It store string data type
let txt = "GeeksforGeeks";
// It store integer data type
let a = 5;
let b = 5;
// It store Boolean data type
(a == b )
// To check Strictly (i.e. Whether the datatypes
// of both variables are same) === is used
(a === b)---> returns true to the console

// It store array data type
let places= [“GFG”, “Computer”, “Hello”];
// It store object data (objects are
// represented in the below way mainly)
let Student = {
firstName:”Johnny”,
lastName:”Diaz”,
age:35,
mark:”blueEYE”}

JavaScript Functions

JavaScript functions are the blocks of code used to perform some particular operations. JavaScript function is executed when something calls it. It calls many times so the function is reusable.

Syntax: 

function functionName( par1, par2, ....., parn ) {  
    // Function code
}  

The JavaScript function can contain zero or more arguments.

Example: This example shows the use of Javascript functions.

Output: 

45