➕bitwise not (~)

🚧 under construction -> code example

JS ⟩ statement ⟩ expression ⟩ operator ⟩ arithmetic ⟩ bitwise ⟩ not

(converts the operand to a 32-bit signed integer)

inverts the bits of its operand. (definition： ~x = -x - 1 , 👉 2's complement)

// ⭐ `~x` === -x - 1 (if x integer, truncate decimal if not)
~(3),       // -4    (-3 - 1)
~(-5),      //  4    ( 5 - 1)

~(3.4),     // -4    ( 3.4 ->  3 -> -3 - 1 = -4)
~(-5.5),    //  4    (-5.5 -> -5 ->  5 - 1 =  4)

// ⭐ `~~x`: nearest integer towards 0.
~~(7.8),    //  7
~~(-3.4),   // -3
~~(6),      //  6 (⭐ `~~x = x`, if x integer)

🌟 table of operators

🗺️ 圖表

• replit： bitwise not (~) (v.2)

┌── (+x !== ~~x)
│
│  x           type        +x              ~~x          ~x      ⭐   
────────────────────────────────────────────────────────────────────
   null        Null                    0            0            -1
⭐ undefined   Undefined             NaN            0            -1
────────────────────────────────────────────────────────────────────
   true        Boolean                 1            1            -2
   false       Boolean                 0            0            -1
────────────────────────────────────────────────────────────────────
   ''          String                  0            0            -1
   '23'        String                 23           23           -24
⭐ 'yes'       String                NaN            0            -1
────────────────────────────────────────────────────────────────────
   1           Number                  1            1            -2
   0           Number                  0            0            -1
⭐ NaN         Number                NaN            0            -1
⭐ Infinity    Number           Infinity            0            -1
⭐ -Infinity   Number          -Infinity            0            -1
────────────────────────────────────────────────────────────────────
⛔ 40n         BigInt          TypeError           40           -41
⛔ Symbol()    Symbol          TypeError    TypeError     TypeError
────────────────────────────────────────────────────────────────────
⭐ ({a:1})     Object                NaN            0            -1
⭐ ({})        Object                NaN            0            -1
────────────────────────────────────────────────────────────────────
   []          Array                   0            0            -1
⭐ [4.5]       Array                 4.5            4            -5
⭐ ['-7.8']    Array                -7.8           -7             6
⭐ [1,2,3]     Array                 NaN            0            -1
────────────────────────────────────────────────────────────────────
⭐ /regex/     RegExp                NaN            0            -1
⭐ new Date    Date        1667543819273   1096508425   -1096508426
⭐ ()=>{}      Function              NaN            0            -1
────────────────────────────────────────────────────────────────────

⭐️ 重點

for n-bit signed integers,

• -x = ~x + 1.

• ~x = -x- 1.

• ~(x± M) ≡ ~x (mod M), where $M=2^n$

👉 2's complement

the following all converted to 0 before applying bitwise not (~) operator.

• null / undefined / false / "" (empty string) / NaN / Infinity

• non-numeric String / non-numeric Array

• other object (except Date)

bitwise not (~)

• ✅ can be used with BigInt.
• ❌ can't be used with Symbol❗

all bitwise operators (except >>>) can be used with Number / BigInt.

👥 相關

• 🌟 2's complement
• 👉 double tilde (~~) - nearest integer towards 0.

💈範例

• replit： bitwise not (~)

// ⭐ test ~x
const M = 2 ** 32;        // 4294967296
const m = M/8;            //  536870912

M,           // 4294967296
m,           //  536870912    (m = M/8)

// ⭐ overflow: 3m + 2m ≡ -3m (mod M)
~~(5*m),     // -1610612736    (overflow)❗
-3*m,        // -1610612736

// ⭐ underflow: -5m ≡ 3m (mod M)
~~(-5*m),    //  1610612736    (underflow)❗
3*m,         //  1610612736
-5*m,        // -2684354560

// ⭐ ~(x ± M) = ~x
~1234,          // -1235
~(1234 - M),    // -1235
~(1234 + M),    // -1235

'----------',

// ⭐ `~x` === -x - 1 (truncate decimal if needed)
~(3),       // -4     (-3 - 1)
~(-5),      //  4     ( 5 - 1)

~(3.4),     // -4     ( 3.4 ->  3 -> -3 - 1 = -4)
~(-5.5),    //  4     (-5.5 -> -5 ->  5 - 1 =  4)

// ⭐ `~~x`: 
~~(7.8),    //  7     (⭐ nearest integer towards 0)
~~(-3.4),   // -3
~~(6),      //  6     (⭐ `~~x = x`, if x integer)

📗 參考

• JavaScript: The Definitive Guide ⟩ 4.8.3 Bitwise Operators

• Cornell ⟩ Two's Complement

📘 手冊

• Bitwise NOT (~)