Feat: add maps filter (#79)

Signed-off-by: Yin Da <yd219913@alibaba-inc.com>
Co-authored-by: Tianxin Dong <dongtianxin.tx@alibaba-inc.com>

util/maps/utils.go

@@ -43,6 +43,17 @@ func Map[K comparable, U any, V any](m map[K]U, fn func(U) V) map[K]V {
 	return _m
 }
 
+// Filter functional filter for map items
+func Filter[K comparable, V any](m map[K]V, fn func(K, V) bool) map[K]V {
+	_m := make(map[K]V, len(m))
+	for key, val := range m {
+		if fn(key, val) {
+			_m[key] = val
+		}
+	}
+	return _m
+}
+
 // Copy return a copy of given map
 func Copy[K comparable, V any](m map[K]V) map[K]V {
 	_m := make(map[K]V)

util/maps/utils_test.go

@@ -43,4 +43,8 @@ func TestUtils(t *testing.T) {
 
 	_m := maps.Copy(m)
 	require.Equal(t, 2, len(_m))
+
+	_m = maps.Filter(m, func(k string, _ int) bool { return k == "a" })
+	_m = maps.Map(_m, func(v int) int { return v + 1 })
+	require.Equal(t, map[string]int{"a": 2}, _m)
 }