var obj = {a:2};
obj instanceof Object
typeof obj === 'object'
obj.a
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
instanceof | |
typeof | |
test attribute |
Test name | Executions per second |
---|---|
instanceof | 4713475.0 Ops/sec |
typeof | 8190906.5 Ops/sec |
test attribute | 8364965.0 Ops/sec |
I'll break down the benchmark test cases and explain what's being tested, compared, and their pros and cons.
Benchmark Test Cases:
The benchmark test cases are designed to compare three different approaches:
instanceof
checktypeof
operator with a string literal ("object"
)Each test case has a unique "Test Name" associated with it, which will help identify the specific scenario being tested.
Options Compared:
instanceof
vs typeof
obj instanceof Object
), we're testing the performance of using the instanceof
operator to check if an object is an instance of a particular constructor (in this case, Object
). This checks for tightness and whether the object's prototype chain matches the expected prototype.typeof obj === 'object'
), we're testing the performance of using the typeof
operator with a string literal to check if an object is an instance of Object
. This can lead to false positives for primitive values (e.g., NaN
, -0
, or true
) that are also "objects".obj.a
)obj
object. This checks the overhead of property access and whether it has any notable impact on performance.Pros and Cons:
instanceof
check:Object
.typeof
operator with string literal ("object"
):instanceof
, as it only checks for a specific type and doesn't need to follow the prototype chain.obj.a
):Library:
The Object
constructor is used in the benchmark, which is a built-in JavaScript library that provides an object creation function. Its purpose is to create new objects with a specified prototype, allowing for inheritance and prototypal inheritance.
Special JS Feature/Syntax:
There are no special JavaScript features or syntaxes mentioned in this benchmark. However, it's worth noting that the use of instanceof
and typeof
operators can be affected by other factors like object freeze, sealer, or proxy optimizations, which might not be explicitly tested here.
Alternatives:
Other alternatives for these tests could include:
constructor.name === 'Object'
) to check if an object is an instance of a particular constructor.Keep in mind that these alternatives might not provide the same level of insight as using instanceof
and typeof
, but they could still be interesting variations on the benchmark tests.