Believemy

JavaScript glossary

Every word of JavaScript explained simply: keywords, built-in objects, methods, errors and concepts. Clear definitions and examples that actually run, to learn and to troubleshoot.
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ABCDEFGHIJ
K
LMNOPQRSTUVW
X
YZ

a

AbortController

addEventListener()

arguments

Array

Array.every()

Array.filter()

Array.find()

Array.flat()

Array.forEach()

Array.map()

Array.push()

Array.reduce()

Array.some()

Array.sort()

Array.splice()

Arrow function

async

await

Axios

b

Babel

Boolean

break

Bundler

c

Call stack

Callback

catch

class

classList

Closure

Code coverage

Coercion (type conversion)

CommonJS

const

continue

Cookie

CORS

createElement()

d

dataset

Date

default

Default parameter

delete

Destructuring

document

e

else

Error

ES module

ESLint

Event delegation

Event loop

Event propagation

export

Express

extends

f

false

fetch()

finally

for

FormData

function

g

Generic

getElementById()

h

Hoisting

i

if

IIFE (immediately invoked function expression)

Immutability

import

import() (dynamic import)

in

includes()

indexOf()

innerHTML

instanceof

IntersectionObserver

j

JSDoc

JSON

l

let

localStorage

Loose equality (==)

m

Map

Math

Memoization

Microtask

Minification

Mock

Mutation

n

new

new Promise

Next.js

Node.js

Node.js

npm

npx

null

Nullish coalescing (??)

Number

o

Object

of

Optional chaining (?.)

p

package.json

Polyfill

Prettier

preventDefault()

Promise

Promise.all()

Promise.race()

Prototypal inheritance

Prototype

Pure function

q

querySelector()

r

RangeError

React

Recursion

Reference vs value

ReferenceError

RegExp

Rest (...)

return

s

Scope

sessionStorage

Set

setInterval()

setTimeout()

Side effect

slice()

Source map

Spread (...)

Stack trace

static

Strict equality (===)

String

String.replace()

String.split()

String.startsWith()

String.trim()

super

switch

Symbol

SyntaxError

t

Template literal

Ternary operator (?:)

textContent

then()

this

this binding

throw

Transpilation

Tree shaking

true

Truthy and falsy

try

TypeError

typeof

TypeScript

u

undefined

Union type

Unit test

v

var

Vite

Vitest

w

Web Worker

Webpack

while

window

y

yield

z

Zod

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