- JavaScript Basics
- JS Home
- JS Syntax
- JS Placements
- JS Output
- JS Statements
- JS Keywords
- JS Comments
- JS Variables
- JS var
- JS let
- JS const
- JS var Vs let Vs const
- JS Operators
- JS Arithmetic Operators
- JS Assignment Operators
- JS Comparison Operators
- JS Logical Operators
- JS Bitwise Operators
- JS Ternary Operator
- JS Operator Precedence
- JS Data Types
- JS typeof
- JS Conditional Statements
- JS Conditional Statement
- JS if Statement
- JS if...else Statement
- JS switch Statement
- JS Loops
- JS for Loop
- JS while Loop
- JS do...while Loop
- JS break Statement
- JS continue Statement
- JS break Vs. continue
- JavaScript Popup Boxes
- JS Dialog Box
- JS alert Box
- JS confirm Box
- JS prompt Box
- JavaScript Functions
- JS Functions
- JS setTimeout() Method
- JS setInterval() Method
- JavaScript Events
- JS Events
- JS onclick Event
- JS onload Event
- JS Mouse Events
- JS onreset Event
- JS onsubmit Event
- JavaScript Arrays
- JS Array
- JS Find Length of Array
- JS Add Elements at Beginning
- JS Add Element at End
- JS Remove First Element
- JS Remove Last Element
- JS Get First Index
- JS Get Last Index
- JS Reverse an Array
- JS Sort an Array
- JS Concatenate Arrays
- JS join()
- JS toString()
- JS from()
- JS Check if Value Exists
- JS Check if Array
- JS Slice an Array
- JS splice()
- JS find()
- JS findIndex()
- JS entries()
- JS every()
- JS fill()
- JS filter()
- JS forEach()
- JS map()
- JavaScript Strings
- JS String
- JS Length of String
- JS Convert to Lowercase
- JS Convert to Uppercase
- JS String Concatenation
- JS search()
- JS indexOf()
- JS search() Vs. indexOf()
- JS match()
- JS match() Vs. search()
- JS replace()
- JS toString()
- JS String()
- JS includes()
- JS substr()
- JS Slice String
- JS charAt()
- JS repeat()
- JS split()
- JS charCodeAt()
- JS fromCharCode()
- JS startsWith()
- JS endsWith()
- JS trim()
- JS lastIndexOf()
- JavaScript Objects
- JS Objects
- JS Boolean Object
- JavaScript Math/Number
- JS Math Object
- JS Math.abs()
- JS Math.max()
- JS Math.min()
- JS Math.pow()
- JS Math.sqrt()
- JS Math.cbrt()
- JS Math.round()
- JS Math.ceil()
- JS Math.floor()
- JS Math.trunc
- JS toFixed()
- JS toPrecision()
- JS Math.random()
- JS Math.sign()
- JS Number.isInteger()
- JS NaN
- JS Number()
- JS parseInt()
- JS parseFloat()
- JavaScript Date and Time
- JS Date and Time
- JS Date()
- JS getFullYear()
- JS getMonth()
- JS getDate()
- JS getDay()
- JS getHours()
- JS getMinutes()
- JS getSeconds()
- JS getMilliseconds()
- JS getTime()
- JS getUTCFullYear()
- JS getUTCMonth()
- JS getUTCDate()
- JS getUTCDay()
- JS getUTCHours()
- JS getUTCMinutes()
- JS getUTCSeconds()
- JS getUTCMilliseconds()
- JS toDateString()
- JS toLocaleDateString()
- JS toLocaleTimeString()
- JS toLocaleString()
- JS toUTCString()
- JS getTimezoneOffset()
- JS toISOString()
- JavaScript Browser Objects
- JS Browser Objects
- JS Window Object
- JS Navigator Object
- JS History Object
- JS Screen Object
- JS Location Object
- JavaScript Document Object
- JS Document Object Collection
- JS Document Object Properties
- JS Document Object Methods
- JS Document Object with Forms
- JavaScript DOM
- JS DOM
- JS DOM Nodes
- JS DOM Levels
- JS DOM Interfaces
- JavaScript Cookies
- JS Cookies
- JS Create/Delete Cookies
- JavaScript Regular Expression
- JS Regular Expression
- JS RegEx .
- JS RegEx \w and \W
- JS RegEx \d and \D
- JS RegEx \s and \S
- JS RegEx \b and \B
- JS RegEx \0
- JS RegEx \n
- JS RegEx \xxx
- JS RegEx \xdd
- JS RegEx Quantifiers
- JS RegEx test()
- JS RegEx lastIndex
- JS RegEx source
- JavaScript Advance
- JS Page Redirection
- JS Form Validation
- JS Validations
- JS Error Handling
- JS Exception Handling
- JS try-catch throw finally
- JS onerror Event
- JS Multimedia
- JS Animation
- JS Image Map
- JS Debugging
- JS Browser Detection
- JS Security
- JavaScript Misc
- JS innerHTML
- JS getElementById()
- JS getElementsByClassName()
- JS getElementsByName()
- JS getElementsByTagName()
- JS querySelector()
- JS querySelectorAll()
- JS document.write()
- JS console.log()
- JS instanceof
- JavaScript Programs
- JavaScript Programs
JavaScript Data Types
JavaScript is a loosely or weakly typed language. Therefore, whatever the value assigned to a variable, the variable changed its typed based on the assigned value.
Or we can say, in JavaScript, there is no need to declare or define the type of variable before its use.
In JavaScript, here are the list of 5 data types based on values:
- string - Used to store string type value like "fresherearth"
- number - Used to store number type value like 120
- boolean - Used to store boolean type value. The two boolean type values are true and false
- object - Used to store object type value like [1, 2, 3, 4, 5]
- function - Used to store function type value like function () {}
For example:
x = "fresherearth"; // x is of string type x = 120; // now x is of number type x = true; // now x is of boolean type
See the above example, there is no need to declare the type of variable before initializing any value of that type.
The JavaScript typeof operator is used to find the type of value/variable. For example:
HTML with JavaScript Code
<!DOCTYPE html> <html> <body> <p id="para1"></p> <p id="para2"></p> <p id="para3"></p> <p id="para4"></p> <p id="para5"></p> <script> document.getElementById("para1").innerHTML = typeof "fresherearth"; document.getElementById("para2").innerHTML = typeof 10; document.getElementById("para3").innerHTML = typeof true; document.getElementById("para4").innerHTML = typeof [1, 2, 3, 4, 5]; document.getElementById("para5").innerHTML = typeof function () {}; </script> </body> </html>
Output
JavaScript allows three keyword that are: var, let, and const to declare a variable.
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