JavaScript Cheatsheet

Variables

var
Declares a variable (function scoped)
let
Declares a block variable
const
Declares a block constant

Data Types

String
Textual data
Number
Numeric data
Boolean
True or false
Array
List of values
Object
Key-value pairs

DOM Manipulation

document.getElementById()
Find element by ID
document.querySelector()
Find first matching element
element.innerHTML
Get or set HTML content
element.style.property
Change CSS style

Events

onclick
The user clicks an HTML element
onchange
An HTML element has been changed
onmouseover
The user moves the mouse over an HTML element
onkeydown
The user pushes a keyboard key