feat: adding HasKey (#477)

* feat: adding HasKey

README.md

@@ -122,6 +122,7 @@ Supported helpers for slices:
 Supported helpers for maps:
 
 - [Keys](#keys)
+- [HasKey](#HasKey)
 - [ValueOr](#valueor)
 - [Values](#values)
 - [PickBy](#pickby)
@@ -989,6 +990,20 @@ keys := lo.Keys(map[string]int{"foo": 1, "bar": 2})
 
 [[play](https://go.dev/play/p/Uu11fHASqrU)]
 
+### HasKey
+
+Returns whether the given key exists.
+
+```go
+exists := lo.HasKey(map[string]int{"foo": 1, "bar": 2}, "foo")
+// true
+
+exists := lo.HasKey(map[string]int{"foo": 1, "bar": 2}, "baz")
+// false
+```
+
+[[play](https://go.dev/play/p/aVwubIvECqS)]
+
 ### Values
 
 Creates an array of the map values.

map.go

@@ -12,6 +12,13 @@ func Keys[K comparable, V any](in map[K]V) []K {
 	return result
 }
 
+// HasKey returns whether the given key exists.
+// Play: https://go.dev/play/p/aVwubIvECqS
+func HasKey[K comparable, V any](in map[K]V, key K) bool {
+	_, ok := in[key]
+	return ok
+}
+
 // Values creates an array of the map values.
 // Play: https://go.dev/play/p/nnRTQkzQfF6
 func Values[K comparable, V any](in map[K]V) []V {

map_test.go

@@ -19,6 +19,17 @@ func TestKeys(t *testing.T) {
 	is.Equal(r1, []string{"bar", "foo"})
 }
 
+func TestHasKey(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	r1 := HasKey(map[string]int{"foo": 1}, "bar")
+	is.False(r1)
+
+	r2 := HasKey(map[string]int{"foo": 1}, "foo")
+	is.True(r2)
+}
+
 func TestValues(t *testing.T) {
 	t.Parallel()
 	is := assert.New(t)