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What are JavaScript Reserved Words and Keywords?

Published on Aug 30,2019 210 Views
13 / 29 Blog from JavaScript

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In any programming language, a reserved word or a reserved identifier is a word that cannot be used as an identifier, such as the name of a variable, function, or label. Thus, it is reserved and cannot be used for defining any of these. This is a syntactic definition, and a reserved word may have no meaning. In this article, we will discuss some of the JavaScript reserved words and their description.

JavaScript Reserved Words

Here is a list of JavaScript Reserved words along with their definition:

Reserved WordsDescription

abstract

Abstract is a non-access modifier which is applicable for classes, methods but not variables.

arguments

Argument is an array-like object lists the arguments and a few other properties.

await

The keyword Await makes JavaScript wait until the promise returns a result.

boolean

Boolean is used as a function to get the value of a variable, object, conditions, expressions, etc. in terms of true or false.

break

It breaks the loop and continues executing the code after the loop.

byte

This uses the javascript typeof() operator to detect what kind of type is variable x and y.

case

The switch statement evaluates an expression. The value of the expression is then compared with the values of each case in the structure.

catch

This statement allows you to define a block of code to be executed if an error occurs in the try block.

char

The char keyword is a data type that is used to store a single character.

class

Classes are another way of writing constructor functions which can be used in order to create a new object using the new keyword.

const

The const keyword is used to declare the constant in the function scope.

continue

Continue statement jumps over one iteration in the loop.

debugger

This statement stops the execution of JavaScript and calls the debugging function.

default

The default keyword can be within a switch statement, or with an export statement.

delete

You can use the delete keyword to delete the value of the property and the property itself.

do

The do/while statement is used when you want to run a loop at least one time.

double 

JavaScript numbers are always stored as double precision floating point numbers

else

It is a part of JavaScript’s Conditional Statements and you can use this to perform different actions based on different conditions.

enum

The enum keyword declares an enumerated type.

eval

The eval() function evaluates or executes an argument.

export

The export statement is used when creating JavaScript modules to export functions, objects, or primitive values from the module.

extends

The extends keyword is used in class declarations or class expressions to create a class which is a child of another class.

false

JavaScript includes a Boolean object to represent true or false. It considers null as false.

final

Final keyword is used to state that a value, class, or method cannot be changed.

finally

The finally statement lets you execute code, after try and catch, regardless of the result.

float

JavaScript numbers are always stored as double-precision floating-point numbers.

for

The for statement creates a loop that is executed as long as a condition is true.

function

A function is a JavaScript procedure that performs a task or calculates a value.

goto

The goto is accomplished in JavaScript using the break and continue keywords.

if

You can use if to specify a block of code to be executed if a specified condition is true.

implements

The implements keyword is used to implement an interface.

import

The import keyword is used to call the function to import the module dynamically.

in

The in operator returns true if the specified property is in the specified object or its prototype chain.

instance of

The instanceof operator in JavaScript is used to check the type of an object at run time.

int

It converts a primitive datatype, string, or array to its integer representation.

interface

The interface keyword is used to declare a special type of class that only contains abstract methods.

let

let allows you to declare variables that are limited to a scope of a block statement, or expression on which it is used.

long

Long represents a 64 bit two’s-complement integer value

native

The native keyword is applied to a method to indicates that the method is implemented in native code.

new

The new keyword constructs and returns an object of a constructor function.

null

Null in JavaScript that signifies ‘no value’ or nonexistence of any value.

package

A package is a directory with one or more modules inside of it and a package.json file wich has metadata about the package.

private

A private function can only be used inside of its parent function or module.

protected

A public function can be used inside or outside of its parent function or module.

public

The protected keyword is an access modifier used for attributes, methods and constructors, making them accessible in the same package and subclasses.

return

Return statements cease execution in a function and return a value to the caller.

short

It is used to represent an integer value in JavaScript.

static

The static keyword defines a static method for a class.

super

The super keyword is used to access and call functions on an object’s parent.

switch

The switch statement evaluates an expression.

synchronized

synchronous code is executed in a sequence where each statement waits for the previous statement to finish before executing.

this

The JavaScript this keyword refers to the object it belongs to.

throw 

Throw is the keyword that is used to raise an exception.

throws 

The throws keyword indicates what exception type may be thrown by a method.

transient 

Transient is a variables modifier used in serialization.

true

Boolean datatype returns either of two values i.e. true or false.

try 

The try statement allows you to define a block of code to be tested for errors while it is being executed.

typeof 

typeof is a JavaScript keyword that will return the type of a variable when you call it.

var 

var is used to declare the variable in JavaScript.

void

The JavaScript void operator evaluates the given expression and then returns a value of undefined.

volatile 

Volatile keyword is a qualifier that is applied to a variable when it is declared.

while 

The while statement creates a loop that is executed while a specified condition is true.

with 

The with statement extends the scope chain for a statement.

yield

The yield keyword returns an IteratorResult object with two properties and value.

With this, we come to the end of this “javascript reserved words” article. I hope you found it informative.

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Got a question for us? Please mention it in the comments section of “JavaScript Reserved Keywords” and we will get back to you.

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