#489 Detect Data Type

Create a function that accurately detects the data type of any JavaScript value. This includes both primitive types and complex object types.

Requirements

1. Basic types – number, string, boolean, undefined, null, symbol, bigint
2. Complex types – array, arraybuffer, map, set, date, function, object
3. Lowercase output – return type names in lowercase
4. Edge cases – handle null vs object, arrays vs objects, etc.

Examples

detectType(1);                    // 'number'
detectType('hello');              // 'string'
detectType(true);                 // 'boolean'
detectType(undefined);            // 'undefined'
detectType(null);                 // 'null'
detectType(Symbol('test'));       // 'symbol'
detectType(123n);                 // 'bigint'

detectType([]);                   // 'array'
detectType(new Map());            // 'map'
detectType(new Set());            // 'set'
detectType(new Date());           // 'date'
detectType(() => {});             // 'function'
detectType(new ArrayBuffer());    // 'arraybuffer'
detectType({});                   // 'object'

Signature

function detectType(value: any): string;

Key Challenges

• null detection – typeof null === 'object' is a JavaScript quirk
• Array vs Object – distinguish between arrays and plain objects
• Built-in objects – detect specific constructor types like Map, Set, Date