30-seconds-of-code/snippets/is.md

is

Checks if the provided value is of the specified type (doesn't work with literals).

Use the instanceof operator to check if the provided value is of the specified type.

const is = (type, val) => val instanceof type;

is(Array, [1]); // true
is(ArrayBuffer, new ArrayBuffer()); // true
is(Map, new Map()); // true
is(RegExp, /./g); // true
is(Set, new Set()); // true
is(WeakMap, new WeakMap()); // true
is(WeakSet, new WeakSet()); // true
is(String, ''); // false
is(String, new String('')); // true
is(Number, 1); // false
is(Number, new Number(1)); // true
is(Boolean, true); // false
is(Boolean, new Boolean(true)); // true