var somenum = 7.3, rounded;
rounded = (0.5 + somenum) | 0;
rounded = ~~ (0.5 + somenum);
rounded = (0.5 + somenum) << 0;
rounded = Math.round(somenum);
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
Or bitwise | |
Double bitwise not | |
Left bitwise shift | |
Math.round |
Test name | Executions per second |
---|---|
Or bitwise | 5587303.5 Ops/sec |
Double bitwise not | 5582126.5 Ops/sec |
Left bitwise shift | 6439524.0 Ops/sec |
Math.round | 7427132.5 Ops/sec |
I'll break down the provided JSON and explain what's being tested, compared, and the pros and cons of different approaches.
Benchmark Definition
The benchmark definition is a simple JavaScript expression that calculates the rounded value of somenum
(a constant with value 7.3) using different methods:
rounded = (0.5 + somenum) | 0;
- This uses the bitwise OR operator (|
) to truncate the result to an integer.rounded = ~~ (0.5 + somenum);
- This uses the bitwise NOT operator (~~
) to perform a signed integer arithmetic and then truncates the result to an integer.rounded = (0.5 + somenum) << 0;
- This uses the left shift operator (<<
) with a shift amount of 0, effectively doing nothing, but is included for completeness.rounded = Math.round(somenum);
- This uses the built-in Math.round()
function to calculate the rounded value.Test Cases
Each test case represents a single execution of one of these expressions. The options being compared are:
(0.5 + somenum) | 0;
~~ (0.5 + somenum);
~~
operator can be confusing for some developers, as it's not immediately clear what it does.(0.5 + somenum) << 0;
Math.round(somenum);
Library Usage
There are no explicit libraries being used in these test cases.
Special JavaScript Features or Syntax
None of the provided expressions use any special JavaScript features or syntax (e.g., async/await, arrow functions, etc.).
Alternatives
Other alternatives for rounding numbers in JavaScript include:
Number.round()
: This is a non-standard function that was available in older versions of JavaScript but has been deprecated.Float32Array.prototype.round()
: This uses the Float32Array
data type to perform rounding operations, which can be more efficient than using the Math.round()
function.In summary, the benchmark tests four different methods for rounding numbers in JavaScript: or bitwise, double bitwise not, left bitwise shift, and Math.round. Each method has its pros and cons, and some might be more suitable for specific use cases or performance requirements.