What is the performance difference between 'for...in' and 'for...of' in JavaScript?

What is the performance difference between 'for...in' and 'for...of' in JavaScript?

The 'for...in' loop iterates over the enumerable properties of an object, while 'for...of' is used for iterating over iterable objects like arrays. Generally, 'for...of' is more efficient for arrays.

Can you give me an example of each?

Sure! For 'for...in':

const obj = {a: 1, b: 2};
for (let key in obj) {
  console.log(key, obj[key]);
}

For 'for...of':

const arr = [1, 2, 3];
for (let value of arr) {
  console.log(value);
}

When should I use one over the other?

Use 'for...in' when you need to iterate over object properties, and 'for...of' when working with arrays or other iterable collections.

Are there any performance benchmarks comparing the two?

Yes, benchmarks show that 'for...of' is generally faster for arrays, especially with large datasets, due to its optimized iteration.