In js, in the past, the Math.floor method was used to round down, but now we see this usage: OR operation interval = interval | 0 Why can we round down in this way? , what are the advantages of this usage compared with Math.floor?
Note that | is not a logical OR, but a bitwise OR (OR).
Some small differences. For example, Math.floor(NaN) still returns NaN. But NaN | 0 returns 0. Another example is Math.floor(Infinity) returns Infinity, but Infinity | 0 returns 0
First of all, S1ngS1ng upstairs is right about those small differences.
In addition, | is a bitwise OR operation. Since when 0 is stored in the memory, all integer bits are filled with 0, so the OR operation is performed based on the binary bit and a numerical value. Regardless of the corresponding bit Whether 0 or 1 is ORed with 0, you will get itself. However, since the number 0 does not have a decimal part in the memory, the decimal part of interval is discarded after the bitwise OR operation. In fact, rounding down is achieved by discarding the decimal part.
Since it is a bit operation, it will be faster than Math.floor().
The real reason is: automatic type conversion within js.
js values are all expressed in 64-bit floating point type. When a value requires bit operations, js will automatically convert it into a 32-bit signedinteger and discard the decimal part.
n|0; n>>0; //The following 0 is only used to ensure that the integer value of n remains unchanged.
Reducing from 64-bit to 32-bit will cause a loss of accuracy. Be careful! , maximum effective range: 2^32/2-1
Both can be achieved, interval = interval | 0 This is a writing technique, it depends on personal preference. It may be that interval = interval | 0 will run faster, and writing code will definitely be faster than Math.floor!
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Note that
|is not a logical OR, but a bitwise OR (OR).Some small differences. For example,
Math.floor(NaN)still returnsNaN. ButNaN | 0returns 0.Another example is
Math.floor(Infinity)returnsInfinity, butInfinity | 0returns 0You can also do this
interval = interval >> 0First of all, S1ngS1ng upstairs is right about those small differences.
In addition,
|is a bitwise OR operation. Since when0is stored in the memory, all integer bits are filled with 0, so the OR operation is performed based on the binary bit and a numerical value. Regardless of the corresponding bit Whether0or1is ORed with0, you will get itself. However, since the number 0 does not have a decimal part in the memory, the decimal part ofintervalis discarded after the bitwise OR operation. In fact, rounding down is achieved by discarding the decimal part.Since it is a bit operation, it will be faster than
Math.floor().The real reason is: automatic type conversion within js.
js values are all expressed in
64-bitfloating point type. When a value requiresbit operations, js will automatically convert it into a32-bit signedinteger and discard the decimal part.n|0; n>>0; //The following 0 is only used to ensure that the integer value of n remains unchanged.
Reducing from 64-bit to 32-bit will cause a loss of accuracy.
Be careful!, maximum effective range: 2^32/2-1Both can be achieved,
interval = interval | 0This is a writing technique, it depends on personal preference. It may be thatinterval = interval | 0will run faster, and writing code will definitely be faster thanMath.floor!