A superset is a set that contains all the elements of another set, and possibly more. Knowing how to check if an array is a superset of another array might come in handy from time to time.
As the mathematical definition refers to a set, duplicates are not considered. This is why using a Set
object is a good idea. Combining it with Array.prototype.every()
and Set.prototype.has()
is all that’s needed to perform the check.
Checking for a subset is as simple as reversing the order of the arguments. Note that you can use this function for any type of iterable, not just arrays.
代码实现
const superset = (a, b) => {
const sA = new Set(a), sB = new Set(b);
return [...sB].every(v => sA.has(v));
};
const subset = (a, b) => superset(b, a);
superset([1, 2, 3, 4], [1, 2, 2]); // true
superset([1, 2, 3, 4], [1, 3, 5]); // false
subset(new Set([1, 2]), new Set([1, 2, 3, 4])); // true
subset(new Set([1, 5]), new Set([1, 2, 3, 4])); // false
[!NOTE]
Future versions of ECMAScript may include a
Set.prototype.isSupersetOf()
andSet.prototype.isSubsetOf()
, which will make this snippet obsolete.
翻译自:https://www.30secondsofcode.org/js/s/superset-subset-of-array