feat: add exists map

mapx/mapx.go

@@ -19,3 +19,9 @@ func Keep[T1 comparable, T2 any](m map[T1]T2, keys ...T1) {
 		}
 	}
 }
+
+// Exists checks if a key exists in a map.
+func Exists[T1 comparable, T2 any](m map[T1]T2, key T1) bool {
+	_, ok := m[key]
+	return ok
+}

mapx/mapx_test.go

@@ -32,3 +32,13 @@ func TestKeep(t *testing.T) {
 		2: "two",
 	}, m)
 }
+
+func TestExists(t *testing.T) {
+	m := map[int]string{
+		1: "one",
+		2: "two",
+		3: "three",
+	}
+	assert.True(t, mapx.Exists(m, 2))
+	assert.False(t, mapx.Exists(m, 4))
+}