- JavaScript Basics
- JavaScript Home
- JavaScript Syntax
- JavaScript Placements
- JavaScript Output
- JavaScript Statements
- JavaScript Keywords
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- JavaScript Variables
- JavaScript var
- JavaScript let
- JavaScript const
- JavaScript var Vs let Vs const
- JavaScript Operators
- JavaScript Arithmetic Operators
- JavaScript Assignment Operators
- JS Comparison Operators
- JavaScript Logical Operators
- JavaScript Bitwise Operators
- JavaScript Ternary Operator
- JavaScript Operator Precedence
- JavaScript Data Types
- JavaScript typeof Operator
- JS Conditional Statements
- JavaScript Conditional Statement
- JavaScript if Statement
- JavaScript if-else Statement
- JavaScript switch Statement
- JavaScript Loops
- JavaScript for Loop
- JavaScript while Loop
- JavaScript do-while Loop
- JavaScript Break Continue
- JavaScript Popup Boxes
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- JavaScript confirm Box
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- JavaScript Functions
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- JS Function with Parameter
- JavaScript Return Statement
- JavaScript Variable Scope
- JavaScript setTimeout() Method
- JavaScript setInterval() Method
- JavaScript Events
- JavaScript Events
- JavaScript onclick Event
- JavaScript onload Event
- JavaScript Mouse Events
- JavaScript onreset Event
- JavaScript onsubmit Event
- JavaScript Objects
- JavaScript Objects
- JavaScript Number Object
- JavaScript Array Object
- JavaScript String Object
- JavaScript Boolean Object
- JavaScript Math Object
- JavaScript RegExp Object
- JavaScript Date Object
- JavaScript Browser Objects
- JavaScript Browser Objects
- JavaScript Window Object
- JavaScript Navigator Object
- JavaScript History Object
- JavaScript Screen Object
- JavaScript Location Object
- JavaScript Document Object
- JS Document Object Collection
- JS Document Object Properties
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- JavaScript DOM
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- JavaScript Create/Delete Cookies
- JavaScript Advance
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- JavaScript Page Redirection
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- JavaScript Error Handling
- JavaScript Exception Handling
- JavaScript try-catch throw finally
- JavaScript onerror Event
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- JavaScript Animation
- JavaScript Image Map
- JavaScript Debugging
- JavaScript Browser Detection
- JavaScript Security
- JavaScript Misc
- JavaScript innerHTML
- JavaScript getElementById()
- JS getElementsByClassName()
- JS getElementsByName()
- JS getElementsByTagName()
- JavaScript querySelector()
- JavaScript querySelectorAll()
- JavaScript document.write()
- JavaScript console.log()
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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 "codescracker"
- 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 = "codescracker"; // 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> <script> document.write(typeof "codescracker", "<BR>"); document.write(typeof 10, "<BR>"); document.write(typeof true, "<BR>"); document.write(typeof [1, 2, 3, 4, 5], "<BR>"); document.write(typeof function () {}, "<BR>"); </script> </body> </html>
Output
JavaScript allows three keyword that are: var, let, and const to declare a variable.
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