Object clone performance: preliminary results
Hi đź‘‹ you're reading a pretty old post! I started writing on here back in high school and this page may not reflect my current views. Recommend checking out related articles and categories down below, I've likely published more recent thoughts on this topic.
Spurred by debate on A Puzzle in JavaScript objects, I wanted to find the best way to clone objects in JavaScript. In this scenario, “best” means “fastest on average”.
I’m using the dataset from this visualization on H1B salaries as a quick way to build many objects. The dataset contains 81,123 objects with 9 keys each.
The experiment is set up like this:
- load & parse data
- run clone experiments in series
- each experiment makes 10 deep copies of the dataset
- “deep” is allowed to mean just the 2 levels required (objects in array don’t contain more objects)
- present average runtime of each clone
Each individual experiment uses this runner:
runner(name, method) {
const times = d3.range(0, this.N).map(() => {
const t1 = new Date();
let copy = method(this.state.data);
const t2 = new Date();
return t2 - t1;
});
let results = this.state.results;
results.push({name: name,
avg: d3.mean(times)});
this.setState({results: results});
}If you spot a problem with that setup, tell me.
Preliminary results, running on my laptop in Chrome 53, are a bit strange. Iterating through the array and doing Object.assign is fastest, and _.cloneDeep is slowest.
I want to add a more context-aware Lodash approach, Immutable.js, and a few different browsers. Then make some graphs :)
What’s your favorite way to clone objects in JavaScript? I’ll add it to the test.
Filed under: ProgrammingJavaScriptTechnical
