左移 (<<)

const a = 5; // 00000000000000000000000000000101
const b = 2; // 00000000000000000000000000000010

console.log(a << b); // 00000000000000000000000000010100
// Expected output: 20

     9 (十进制): 00000000000000000000000000001001 (二进制)
                 --------------------------------

9 << 2 (十进制): 00000000000000000000000000100100 (二进制) = 36 (十进制)

9 << 3; // 72

// 9 * 2³ = 9 * 8 = 72