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JavaScript Cheat Sheet
Print-ready cheat sheet for JavaScript, organized for fast lookup, study, and desk-side use
Sample
What's in this cheat sheet
Variables
let name = "Alice"; // reassignable
const PI = 3.14; // constant
var old = "avoid"; // function-scoped (legacy)
Data Types
string | Text: `"hello"` or `'hello'` |
number | Integer or float: `42`, `3.14` |
boolean | `true` / `false` |
null | Intentional empty value |
undefined | Declared but not assigned |
object | Key-value pairs: `{ a: 1 }` |
array | Ordered list: `[1, 2, 3]` |
Type Checking & Conversion
typeof "hello" // "string"
typeof 42 // "number"
Number("42") // 42
String(100) // "100"
parseInt("3.9") // 3
parseFloat("3.14") // 3.14
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