In JavaScript, all integer variables are signed integers by default. What does this mean?
Signed integers use 31 bits to represent the value of an integer, 32th bits to represent the symbol of an integer, 0 represents a positive number, and 1 represents a negative number.
The values range from -2^31 - 2^31-1 that is -2147483648 to 2147483647.
When JavaScript performs bit operations, it uses 32-bit signed integers, which means that the result of its conversion is also a 32-bit signed integer. Sometimes, when we shift, we will have unexpected results. The following is a comparison between C and JS.
C language
unsigned int a = 3774191835u;
unsigned int b = a >> 2;
/* b == 943547958 */
JavaScript
var a = 3774191835;
var b = a >> 2;
/* b == -130193866 */
It can be seen that when JavaScript performs bit operations, it uses signed integers, so we get different results. How to solve it?
We can convert signed numbers in JavaScript into unsigned numbers. Just perform >>>0 shift operation.
It is best not to use >> , it is recommended to use >>> because the leftmost bit will be parsed into a sign bit, and when the number overflows, it will be parsed into a negative number.
Signed integers use 31 bits to represent the value of an integer, 32th bits to represent the symbol of an integer, 0 represents a positive number, and 1 represents a negative number.
The values range from -2^31 - 2^31-1 that is -2147483648 to 2147483647.
When JavaScript performs bit operations, it uses 32-bit signed integers, which means that the result of its conversion is also a 32-bit signed integer. Sometimes, when we shift, we will have unexpected results. The following is a comparison between C and JS.
C language
Copy the codeThe code is as follows:
unsigned int a = 3774191835u;
unsigned int b = a >> 2;
/* b == 943547958 */
JavaScript
Copy the codeThe code is as follows:
var a = 3774191835;
var b = a >> 2;
/* b == -130193866 */
It can be seen that when JavaScript performs bit operations, it uses signed integers, so we get different results. How to solve it?
We can convert signed numbers in JavaScript into unsigned numbers. Just perform >>>0 shift operation.
It is best not to use >> , it is recommended to use >>> because the leftmost bit will be parsed into a sign bit, and when the number overflows, it will be parsed into a negative number.