all

Checks if the provided predicate function returns true for all elements in a collection.

• Use Array.prototype.every() to test if all elements in the collection return true based on fn.
• Omit the second argument, fn, to use Boolean as a default.

const all = (arr, fn = Boolean) => arr.every(fn);

all([4, 2, 3], x => x > 1); // true
all([1, 2, 3]); // true