var n ={};
if(!n.foo) {
}
if(n.foo===undefined)
{
}
if(!Object.hasOwn(n,'foo'))
{
}
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
test truth | |
test undefined | |
test hasOwnProperty |
Test name | Executions per second |
---|---|
test truth | 1771618304.0 Ops/sec |
test undefined | 1736551424.0 Ops/sec |
test hasOwnProperty | 1569789824.0 Ops/sec |
Let's break down the provided benchmark definition and test cases to understand what is being tested.
Benchmark Definition
The main goal of this benchmark is to compare the performance benefits of using different methods to check for the existence or absence of a property in an object.
The script preparation code creates an empty object n
with no properties. The benchmark tests three scenarios:
test truth
: Verifies that accessing an non-existent property (n.foo
) returns false.test undefined
: Verifies that comparing n.foo
to undefined
returns true.test hasOwnProperty
: Verifies that using the hasOwnProperty
method on the object checks for the existence of a specific property.Options Compared
The benchmark compares two approaches:
!
operator: Checks if a property exists by negating its value, e.g., n.foo
.=== undefined
comparison: Directly compares the value to undefined
, e.g., n.foo === undefined
.Pros and Cons of Each Approach
!
Operator!
operator.=== undefined
ComparisonOther Considerations
The benchmark assumes that modern JavaScript engines will optimize these comparisons in a similar way. However, there might be subtle differences between different browsers or engines.
Additionally, it's worth noting that using hasOwnProperty
can be slower than other approaches due to the method call overhead. Nevertheless, it provides explicit information about the property's existence and is often considered more readable.
Library Usage
In this benchmark, no external libraries are used. However, some browsers (like Firefox) may use internal libraries or optimizations that are not explicitly mentioned in the benchmark definition.
Special JS Features or Syntax
None of the test cases explicitly use special JavaScript features like let
, const
, or arrow functions. The syntax is straightforward and focused on demonstrating the property existence checks.
In summary, this benchmark aims to compare the performance benefits of using different methods to check for property existence in an object, highlighting the pros and cons of each approach.