The Array.prototype.every() method always returns true for an empty array

My friend Nicholas Zakas made an interesting observation on Mastodon this week: the Array.prototype.every() method always returns true for an empty array.

let arr = [];

// Returns true
arr.every(function (item) {
	return false;
});

// Also returns true
arr.every(function (item) {
	return true;
});

Axel Rauschmayer provided an interesting explanation…

.every() implements universal quantification (“for all”, ∀). And that operator is always true for empty sets…

That is also how we understand [for all] intuitively if we use it in natural language: “All humans that live on Venus have blue skin” is true (because no humans live on Venus).