var obj = {
'a': 1,
'b': 1,
'c': 1,
'd': 1,
'e': 1,
'f': 1,
'g': 1
};
for (var i=10000; i > 0; i--) {
var k = 0;
for (var key in obj) {
k++;
}
}
for (var i=10000; i > 0; i--) {
Object.keys(obj).length;
}
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
for-in | |
Object.keys |
Test name | Executions per second |
---|---|
for-in | 1284.5 Ops/sec |
Object.keys | 494.1 Ops/sec |
Let's dive into the world of JavaScript microbenchmarks and analyze the provided benchmark definition.
What is being tested?
The two individual test cases are designed to compare the performance of two approaches for iterating over an object:
for-in
Object.keys()
method with property lengthBoth tests aim to measure how many times a loop iterates over the keys of the same object, obj
, which contains 7 properties.
Options compared
The two options being compared are:
for-in
: A traditional loop using for
keyword that iterates over the object's properties directly.Object.keys()
: A method that returns an array-like object containing all the property names of the given object, allowing for iteration over the keys.Pros and Cons
for-in
, as it only iterates over property names without considering their values or prototype chain.for-in
.Object.keys()
method, which may introduce a small overhead due to function call and string lookup.Library usage
The Object.keys()
method is a built-in JavaScript method that returns an array-like object containing all the property names of the given object. This method does not rely on any external libraries or frameworks.
Special JS features or syntax
There are no special JavaScript features or syntax used in these test cases, only standard language constructs and built-in methods.
Other alternatives
If you were to consider alternative approaches for iterating over an object's properties, some options could be:
for...in
with a custom loop iterator (e.g., using Object.keys()
internally).Symbol.iterator
, Array.from()
, or Object.entries()
methods.lodash
or fast-objects
.In the context of this benchmark, however, for-in
and Object.keys()
are sufficient to compare their performance, and other alternatives would likely introduce unnecessary complexity.
Keep in mind that the choice of iteration method ultimately depends on the specific requirements and constraints of your use case.