var value = 2;
typeof value !== 'undefined'
value !== void 0
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
typeof | |
void 0 |
Test name | Executions per second |
---|---|
typeof | 10891501.0 Ops/sec |
void 0 | 10590432.0 Ops/sec |
Let's break down what's being tested in this benchmark and the pros and cons of each approach.
Benchmark Definition
The benchmark definition is a JSON object that defines the benchmark's name, description, script preparation code, and HTML preparation code. However, there are no options to compare in this case.
Instead, we have two individual test cases:
typeof value !== 'undefined'
value !== void 0
What are typeof
and void 0
?
typeof
is a JavaScript operator that returns the data type of a variable or expression. In this case, it's used to check if the value
variable has been initialized.void 0
is an older syntax for checking if a value is not null or undefined (equivalent to typeof value !== 'undefined'
). The void
keyword is used as a "null coalescing" operator in this context.Options comparison
The options being compared are:
typeof value !== 'undefined'
value !== void 0
Both expressions achieve the same result: checking if value
has been initialized. However, there's a subtle difference:
typeof
is more explicit and readable.void 0
is older syntax that was used in JavaScript before the typeof
operator became widely adopted.Pros and Cons
Pros of using typeof
:
Cons of using typeof
:
Pros of using void 0
:
Cons of using void 0
:
Other considerations
In general, when deciding between these two options, consider the following:
typeof
.void 0
.Keep in mind that both expressions have equivalent results and are widely supported.
Other alternatives
If you want to explore other ways of checking if a value is initialized, consider the following options:
if
statement: if (value !== null && value !== undefined) { ... }
?.
): value?.toString()
?:
): (value ? 'initialized' : 'not initialized')
However, these alternatives may have their own trade-offs and may not be as widely supported or efficient as the original two options.