JS shift operators (< <,> > and > > >)

JS Shift Operators （<<、>> and >>>）

Shift operation is to perform regular low shift on binary . Shift operation can design many wonderful effects , It is widely used in graphics and image programming .

“<<” Operator

“<<” Operator performs a left shift operation . During the shift operation , The sign bit remains unchanged . If the right side is empty , Is automatically filled with 0; beyond 32 The value of a , Automatically discard .
for example ： Put the numbers 5 Move to the left 2 position , The return value is 20.

console.log(5 << 2); // Return value 20
Demonstrate with a formula , As shown in the figure .

“>>” Operator

“>>” Operator performs a signed right shift operation . Opposite to the left shift operation , It is the 32 All significant bits in the bit number are shifted to the right as a whole , Then fill the empty bit with the value of the sign bit . Values exceeded during the move will be discarded .
For example, put the value 1000 Move right 8 position , The return value is 3.

console.log(1000 >> 8); // Return value 3

Demonstrate with a formula , As shown in the figure .

Put the number -1000 Move right 8 position , The return value is -4.

console.log(-1000 >> 8); // Return value -4

Demonstrate with a formula , As shown in the figure . When the sign bit value is 1 when , Then all the empty bits on the left side of the significant bit are used 1 Fill in .

“>>>” Operator

“>>>” Operator performs an unsigned shift right operation . It takes the unsigned 32 Bit integers all bits are shifted to the right as a whole . For the shift right operation of an unsigned number or a positive number , The result of the shift right operation is the same as that of the shift right operation .

The return value of the following two lines of expression is the same .

console.log(1000 >> 8); // Return value 3
console.log(1000 >> 8); // Return value 3

For negative numbers , Move right without sign will use 0 To fill all the vacancies , At the same time, negative numbers are treated as positive numbers , The results will be very large, so , Be very careful when using the unsigned shift right operator , Avoid unexpected mistakes .

console.log(-1000 >> 8); // Return value -4
console.log(-1000 >>> 8); // Return value
16777212

Demonstrate with a formula , As shown in the figure . The left vacancy is no longer filled with the value of the sign bit , It's about using 0 Fill in .