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Coding — JavaScript Fundamentals

Core JavaScript concepts for beginners and review

J
js_nocap 15 terms Mar 9, 2026
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Terms 15

1
var
Function-scoped variable declaration; hoisted; generally avoid in modern JS
2
let
Block-scoped variable declaration; can be reassigned
3
const
Block-scoped constant; cannot be reassigned; preferred default
4
Arrow Function
Concise function syntax: (x) => x * 2; inherits 'this' from outer scope
5
Callback
Function passed as argument to another function; called after operation completes
6
Promise
Object representing eventual completion or failure of async operation
7
async/await
Syntax for writing asynchronous code that looks synchronous; built on Promises
8
DOM
Document Object Model; JavaScript's representation of HTML elements
9
Event Listener
Function attached to element waiting for specific event to fire
10
Closure
Function that retains access to its outer function's scope after outer function returns
11
Hoisting
Variable and function declarations moved to top of scope before execution
12
Truthy/Falsy
Values treated as true or false in boolean context; 0, '', null, undefined are falsy
13
Spread Operator
... syntax expanding iterable into individual elements
14
Destructuring
Extracting values from arrays/objects into distinct variables
15
JSON
JavaScript Object Notation; text format for data exchange