var map = {};
function generateSequence(prefix, numItems) {
var buffer = [];
var prefixInstance = prefix || "";
for (var i = 0; i < numItems; i++) {
buffer.push(prefix + i);
}
return buffer;
}
var startTime;
function startTimer() {
startTime = new Date().getTime()
}
function stopTimer() {
var endTime = new Date().getTime();
console.log("Took " + (endTime - startTime) + " ms");
}
function generateMap() {
console.log("Generating");
for (var i = 0; i < 50000; i++) {
map["a-" + i] = {
a: generateSequence("aaaaaaaaa", 10)
}
}
}
generateMap();
console.log("Test #1");
startTimer();
for (key in map) {
if (map.hasOwnProperty(key)) {
delete map[key];
}
}
stopTimer();
generateMap();
console.log("Test #2");
startTimer();
var keys = Object.keys(map);
for (var i = 0, ii = keys.length; i < ii; i++) {
delete map[keys[i]];
}
stopTimer();
--enable-precise-memory-info
flag.
Test case name | Result |
---|---|
The slow version | |
Faster version using Object.keys(). |
Test name | Executions per second |
---|---|
The slow version | 7.3 Ops/sec |
Faster version using Object.keys(). | 9.9 Ops/sec |
Let's break down the provided benchmark and explain what's being tested.
Benchmark Definition
The benchmark is designed to test the performance of deleting a large map in JavaScript, specifically between two approaches: using the for...in
loop with hasOwnProperty()
(Test #1) and using Object.keys()
(Test #2).
Options Compared
The two options being compared are:
for...in
loop with hasOwnProperty()
to iterate over the map's keys and delete each key-value pair.for (var i = 0; i < numItems; i++) {
buffer.push(prefix + i);
}
Object.keys()
to get an array of the map's keys, then iterating over that array using a traditional for
loop to delete each key-value pair.var keys = Object.keys(map);
for (var i = 0, ii = keys.length; i < ii; i++) {
delete map[keys[i]];
}
Pros and Cons of Each Approach
for...in
loop with hasOwnProperty()
has a few advantages:hasOwnProperty()
check adds extra overhead, especially when the map is large.Object.keys()
provides a more modern and expressive way to iterate over the map's keys:for...in
loop with hasOwnProperty()
.Object.keys()
method may not be supported in older browsers or environments.Library Usage
The benchmark uses the generateSequence
function to generate a large sequence of strings, but it does not use any external libraries. However, it does rely on the built-in Date
object and the console.log()
function for logging purposes.
Special JS Feature or Syntax
There are no special JavaScript features or syntax used in this benchmark, aside from the modern usage of Object.keys()
which is a relatively recent addition to the language.
Alternative Approaches
Other approaches to deleting a large map could include:
forEach()
with a callback functionpick()
or omit()
These alternatives may offer different trade-offs in terms of performance, readability, and maintainability, depending on the specific use case and requirements.