➕remainder (%)

remainder `r = a % b`, `r` has the same sign as `a`.

JS ⟩ operator ⟩ arithmetic ⟩ remainder (%)

a%b returns

• NaN, if one of the operands is NaN /a = ±Infinity / b = ±0.

• a, if a = ±0 /b = ±Infinity.

• r=a-b*q where：

  • q is the integer such that：

  • r has the same sign asa, while being as close to 0 as possible.

// ⭐️ `a` decides the sign of the remainder
 5 % 2    //  1
-5 % 2    // -1   

👉 table of operators, remainder vs. modulo vs. mod

⭐️ 重點

⭐ remainder (%) and modulo are different❗ 👉 remainder vs. modulo vs. mod

% operator

• works for floating-point numbers too.

👥 相關

• modulo(a, b)

• mod(a, b)

💈範例

• replit： modulo(a,b) vs. mod(a,b)

// ⭐️ remainder (a % b)
//
// ┌─── `a` decides the "sign" ⭐️
// │
   5 %  3,    //  2
   5 % -3,    //  2
  -5 %  3,    // -2
  -5 % -3,    // -2

// modulo(a, b)
//          ┌─── `b` decides the "sign" ⭐️
//          │ 
modulo( 5,  3),    //  2
modulo( 5, -3),    // -1
modulo(-5,  3),    //  1
modulo(-5, -3),    // -2

modulo(6.4, 2.3),     //  1.8000000000000007

// mod(a, b) (in math)
//                    ┌─── always >= 0 ⭐️
//                    │ 
mod( 5,  3),       // 2
mod( 5, -3),       // 2
mod(-5,  3),       // 1
mod(-5, -3),       // 1

📗 參考

• JavaScript: The Definitive Guide ⟩ 4.8

📘 手冊

• Remainder (%)