🔰type conversion

JS ⟩ value ⟩ type ⟩ conversion

When JS expects a boolean, a value of any type can be supplied, and JS will convert it as needed. The same is true for all types.

// ⭐ explicit type conversion
Number(' 012'),    // 12
String(34),        // '34'
Boolean({}),       // true

// ⭐ implicit type conversion
+' 012',    // === Number(' 012')
34 + '',    // === String(34)
!!{},       // === Boolean({})

replit： type conversion table (require： TableMaker)

┌── (primitive?)
│                              (-> number)   (-> string)
│  x          desc                    +x     String(x)
────────────────────────────────────────────────────────────────────
✅ null                                  0   "null"                 
────────────────────────────────────────────────────────────────────
✅ undefined

isNaN(x) will try to convert x to a number first❗
Number.isNaN(x) never do conversions.

any to .

any value has method, usually equivalent to ().

replit： type conversion examples

let n = NaN;

8 + " cats",    // "8 cats"   (8 -> '8')
n + " dogs",    // "NaN dogs" (NaN -> 'NaN')

'3' * '8',      // 24         ('3' -> 3, '8' -> 8)
4 - "a",        // NaN        ('a' -> NaN)

Previousdynamically typed Nexttype name

Last updated 2 years ago

Was this helpful?

// ⭐ explicit type conversion Number(' 012'), // 12 String(34), // '34' Boolean({}), // true // ⭐ implicit type conversion +' 012', // === Number(' 012') 34 + '', // === String(34) !!{}, // === Boolean({})

┌── (primitive?) │ (-> number) (-> string) │ x desc +x String(x) ──────────────────────────────────────────────────────────────────── ✅ null 0 "null" ──────────────────────────────────────────────────────────────────── ✅ undefined