diff --git a/README.md b/README.md
index c0a16d3..dc88af4 100644
--- a/README.md
+++ b/README.md
@@ -396,8 +396,8 @@ func Contain[T comparable](slice []T, value T) bool //check if the value is in t
 func Chunk[T any](slice []T, size int) [][]T //creates an slice of elements split into groups the length of size.
 func ConvertSlice(originalSlice interface{}, newSliceType reflect.Type) interface{} //convert originalSlice to newSliceType
 func Difference[T comparable](slice1, slice2 []T) []T //creates an slice of whose element not included in the other given slice
-func DeleteByIndex(slice interface{}, start int, end ...int) (interface{}, error) //delete the element of slice from start index to end index - 1
-func Drop(slice interface{}, n int) interface{} //creates a slice with `n` elements dropped from the beginning when n > 0, or `n` elements dropped from the ending when n < 0
+func DeleteByIndex[T any](slice []T, start int, end ...int) []T //delete the element of slice from start index to end index - 1
+func Drop[T any](slice []T, n int) []T //creates a slice with `n` elements dropped from the beginning when n > 0, or `n` elements dropped from the ending when n < 0
 func Every[T any](slice []T, fn func(index int, t T) bool) bool  //return true if all of the values in the slice pass the predicate function
 func None[T any](slice []T, fn func(index int, t T) bool) bool // return true if all the values in the slice mismatch the criteria
 func Filter [T any] (slice []T, fn func(index int, t T) bool) []T //filter slice, fn signature should be func(int, T) bool.
@@ -406,8 +406,8 @@ func FlattenDeep(slice interface{}) interface{} //flattens slice recursive
 func ForEach [T any] (slice []T, fn func(index int, t T)) //iterates over elements of slice and invokes function for each element, fn signature should be func(int, T ).
 func IntSlice(slice interface{}) ([]int, error) //convert value to int slice
 func InterfaceSlice(slice interface{}) []interface{} //convert value to interface{} slice
-func Intersection(slices ...interface{}) interface{} //creates a slice of unique values that included by all slices.
-func InsertByIndex(slice interface{}, index int, value interface{}) (interface{}, error) //insert the element into slice at index.
+func Intersection[T comparable](slices ...[]T) []T //creates a slice of unique values that included by all slices.
+func InsertByIndex[T any](slice []T, index int, value interface{}) []T //insert the value or other slice into slice at index.
 func Map [T any, U any] (slice []T, fn func(index int, t T) U) []U //map lisce, fn signature should be func(int, T).
 func Reverse[T any](slice []T)//revere slice
 func Reduce[T any](slice []T, fn func(index int, t1, t2 T) T, initial T) T //reduce slice
@@ -415,10 +415,10 @@ func Shuffle[T any](slice []T) []T  //creates an slice of shuffled values
 func SortByField(slice interface{}, field string, sortType ...string) error //sort struct slice by field
 func Some[T any](slice []T, fn func(index int, t T) bool) bool //return true if any of the values in the list pass the predicate fn function
 func StringSlice(slice interface{}) []string //convert value to string slice
-func Unique(slice interface{}) interface{} //remove duplicate elements in slice
-func Union(slices ...interface{}) interface{} //Union creates a slice of unique values, in order, from all given slices. using == for equality comparisons.
-func UpdateByIndex(slice interface{}, index int, value interface{}) (interface{}, error) //update the slice element at index.
-func Without(slice interface{}, values ...interface{}) interface{} //creates a slice excluding all given values
+func Unique[T comparable](slice []T) []T //remove duplicate elements in slice
+func Union[T comparable](slices ...[]T) []T //Union creates a slice of unique values, in order, from all given slices. using == for equality comparisons.
+func UpdateByIndex[T any](slice []T, index int, value T) []T //update the slice element at index.
+func Without[T comparable](slice []T, values ...T) []T //creates a slice excluding all given values
 func GroupBy(slice, function interface{}) (interface{}, interface{}) // groups slice into two categories
 func Count[T any](slice []T, fn func(index int, t T) bool) int // Count iterates over elements of slice, returns a count of all matched elements
 ```
diff --git a/README_zh-CN.md b/README_zh-CN.md
index ca085b1..4dd04de 100644
--- a/README_zh-CN.md
+++ b/README_zh-CN.md
@@ -397,8 +397,8 @@ func Contain[T comparable](slice []T, value T) bool //判断slice是否包含val
 func Chunk[T any](slice []T, size int) [][]T //均分slice
 func ConvertSlice(originalSlice interface{}, newSliceType reflect.Type) interface{} //将originalSlice转换为 newSliceType
 func Difference[T comparable](slice1, slice2 []T) []T //返回切片，其元素在slice1中，不在slice2中
-func DeleteByIndex(slice interface{}, start int, end ...int) (interface{}, error) //删除切片中start到end位置的值
-func Drop(slice interface{}, n int) interface{} //创建一个新切片，当n大于0时删除原切片前n个元素，当n小于0时删除原切片后n个元素
+func DeleteByIndex[T any](slice []T, start int, end ...int) []T //删除切片中start到end位置的值(不包含end)
+func Drop[T any](slice []T, n int) []T //创建一个新切片，当n大于0时删除原切片前n个元素，当n小于0时删除原切片后n个元素
 func Every[T any](slice []T, fn func(index int, t T) bool) bool //slice中所有元素都符合函数条件时返回true, 否则返回false. 函数签名：func(index int, t T) bool
 func None[T any](slice []T, fn func(index int, t T) bool) bool //slice中所有元素都不符合函数条件时返回true, 否则返回false. 函数签名：func(index int, value interface{}) bool
 func Find[T any](slice []T, fn func(index int, t T) bool) (*T, bool)//查找slice中第一个符合条件的元素，函数签名：func(index int, value interface{}) bool
@@ -407,19 +407,19 @@ func FlattenDeep(slice interface{}) interface{} //将slice递归为一维切片
 func ForEach [T any] (slice []T, fn func(index int, t T)) //遍历切片，在每个元素上执行函数
 func IntSlice(slice interface{}) ([]int, error) //转成int切片
 func InterfaceSlice(slice interface{}) []interface{} //转成interface{}切片
-func Intersection(slices ...interface{}) interface{} //slice交集，去重
-func InsertByIndex(slice interface{}, index int, value interface{}) (interface{}, error) //在切片中index位置插入value
-func Map(slice, function interface{}) interface{} //遍历切片, 函数签名：func(index int, value interface{}) interface{}
+func Intersection[T comparable](slices ...[]T) []T //slice交集，去重
+func InsertByIndex[T any](slice []T, index int, value interface{}) []T //在切片中index位置插入value
+func Map [T any, U any] (slice []T, fn func(index int, t T) U) []U //遍历切片
 func Reverse[T any](slice []T) //反转切片
 func Reduce[T any](slice []T, fn func(index int, t1, t2 T) T, initial T) T //切片reduce操作
 func Shuffle[T any](slice []T) []T  //创建一个被打乱值的切片
 func Some[T any](slice []T, fn func(index int, t T) bool) bool //slice中任意一个元素都符合函数条件时返回true, 否则返回false.
 func SortByField(slice interface{}, field string, sortType ...string) error //对struct切片进行排序
 func StringSlice(slice interface{}) []string //转为string切片
-func Unique(slice interface{}) interface{} //去重切片
-func Union(slices ...interface{}) interface{} //slice并集, 去重
-func UpdateByIndex(slice interface{}, index int, value interface{}) (interface{}, error) //在切片中index位置更新value
-func Without(slice interface{}, values ...interface{}) interface{} //slice去除values
+func Unique[T comparable](slice []T) []T //去重切片
+func Union[T comparable](slices ...[]T) []T //slice并集, 去重
+func UpdateByIndex[T any](slice []T, index int, value T) []T //在切片中index位置更新value
+func Without[T comparable](slice []T, values ...T) []T //slice去除values
 func GroupBy(slice, function interface{}) (interface{}, interface{}) //根据函数function的逻辑分slice为两组slice
 func Count[T any](slice []T, fn func(index int, t T) bool) int //遍历slice的元素，返回所有匹配元素的计数
 ```
diff --git a/slice/slice.go b/slice/slice.go
index 59b2f2b..a8089ba 100644
--- a/slice/slice.go
+++ b/slice/slice.go
@@ -5,7 +5,6 @@
 package slice
 
 import (
-	"errors"
 	"fmt"
 	"math"
 	"math/rand"
@@ -216,7 +215,7 @@ func flattenRecursive(value reflect.Value, result reflect.Value) reflect.Value {
 }
 
 // ForEach iterates over elements of slice and invokes function for each element
-// The fn signature should be func(int, T).
+// The fn function signature should be func(int, T).
 func ForEach[T any](slice []T, fn func(index int, t T)) {
 	for i, v := range slice {
 		fn(i, v)
@@ -224,7 +223,7 @@ func ForEach[T any](slice []T, fn func(index int, t T)) {
 }
 
 // Map creates an slice of values by running each element of slice thru fn function.
-// The fn signature should be func(int, T).
+// The fn function signature should be func(int, T).
 func Map[T any, U any](slice []T, fn func(index int, t T) U) []U {
 	res := make([]U, len(slice), cap(slice))
 	for i, v := range slice {
@@ -321,107 +320,87 @@ func ConvertSlice(originalSlice interface{}, newSliceType reflect.Type) interfac
 }
 
 // DeleteByIndex delete the element of slice from start index to end index - 1.
-// Delete i: s = append(s[:i], s[i+1:]...)
-// Delete i to j: s = append(s[:i], s[j:]...)
-func DeleteByIndex(slice interface{}, start int, end ...int) (interface{}, error) {
-	v := sliceValue(slice)
-	i := start
-	if v.Len() == 0 || i < 0 || i > v.Len() {
-		return nil, errors.New("InvalidStartIndex")
-	}
-	if len(end) > 0 {
-		j := end[0]
-		if j <= i || j > v.Len() {
-			return nil, errors.New("InvalidEndIndex")
-		}
-		v = reflect.AppendSlice(v.Slice(0, i), v.Slice(j, v.Len()))
-	} else {
-		v = reflect.AppendSlice(v.Slice(0, i), v.Slice(i+1, v.Len()))
-	}
+func DeleteByIndex[T any](slice []T, start int, end ...int) []T {
+	size := len(slice)
 
-	return v.Interface(), nil
-}
-
-// Drop creates a slice with `n` elements dropped from the beginning when n > 0, or `n` elements dropped from the ending when n < 0
-func Drop(slice interface{}, n int) interface{} {
-	sv := sliceValue(slice)
-
-	if n == 0 {
+	if start < 0 || start > size-1 {
 		return slice
 	}
 
-	svLen := sv.Len()
-
-	if math.Abs(float64(n)) >= float64(svLen) {
-		return reflect.MakeSlice(sv.Type(), 0, 0).Interface()
-	}
-
-	if n > 0 {
-		res := reflect.MakeSlice(sv.Type(), svLen-n, svLen-n)
-		for i := 0; i < res.Len(); i++ {
-			res.Index(i).Set(sv.Index(i + n))
+	if len(end) > 0 {
+		end := end[0]
+		if end <= start {
+			return slice
+		}
+		if end > size {
+			end = size
 		}
 
-		return res.Interface()
+		slice = append(slice[:start], slice[end:]...)
+		return slice
 	}
 
-	res := reflect.MakeSlice(sv.Type(), svLen+n, svLen+n)
-	for i := 0; i < res.Len(); i++ {
-		res.Index(i).Set(sv.Index(i))
+	if start == size-1 {
+		slice = append(slice[:start])
+	} else {
+		slice = append(slice[:start], slice[start+1:]...)
 	}
 
-	return res.Interface()
+	return slice
 }
 
-// InsertByIndex insert the element into slice at index.
-// Insert value: s = append(s[:i], append([]T{x}, s[i:]...)...)
-// Insert slice: a = append(a[:i], append(b, a[i:]...)...)
-func InsertByIndex(slice interface{}, index int, value interface{}) (interface{}, error) {
-	v := sliceValue(slice)
+// Drop creates a slice with `n` elements dropped from the beginning when n > 0, or `n` elements dropped from the ending when n < 0
+func Drop[T any](slice []T, n int) []T {
+	size := len(slice)
 
-	if index < 0 || index > v.Len() {
-		return slice, errors.New("InvalidSliceIndex")
+	if size == 0 || n == 0 {
+		return slice
 	}
 
-	// value is slice
-	vv := reflect.ValueOf(value)
-	if vv.Kind() == reflect.Slice {
-		if reflect.TypeOf(slice).Elem() != reflect.TypeOf(value).Elem() {
-			return slice, errors.New("InvalidValueType")
-		}
-		v = reflect.AppendSlice(v.Slice(0, index), reflect.AppendSlice(vv.Slice(0, vv.Len()), v.Slice(index, v.Len())))
-		return v.Interface(), nil
+	if math.Abs(float64(n)) >= float64(size) {
+		return []T{}
 	}
 
-	// value is not slice
-	if reflect.TypeOf(slice).Elem() != reflect.TypeOf(value) {
-		return slice, errors.New("InvalidValueType")
-	}
-	if index == v.Len() {
-		return reflect.Append(v, reflect.ValueOf(value)).Interface(), nil
+	if n < 0 {
+		return slice[0 : size+n]
 	}
 
-	v = reflect.AppendSlice(v.Slice(0, index+1), v.Slice(index, v.Len()))
-	v.Index(index).Set(reflect.ValueOf(value))
+	return slice[n:size]
+}
 
-	return v.Interface(), nil
+// InsertByIndex insert the value or other slice into slice at index.
+func InsertByIndex[T any](slice []T, index int, value interface{}) []T {
+	size := len(slice)
+
+	if index < 0 || index > size {
+		return slice
+	}
+
+	// value is T
+	if v, ok := value.(T); ok {
+		slice = append(slice[:index], append([]T{v}, slice[index:]...)...)
+		return slice
+	}
+
+	// value is []T
+	if v, ok := value.([]T); ok {
+		slice = append(slice[:index], append(v, slice[index:]...)...)
+		return slice
+	}
+
+	return slice
 }
 
 // UpdateByIndex update the slice element at index.
-func UpdateByIndex(slice interface{}, index int, value interface{}) (interface{}, error) {
-	v := sliceValue(slice)
+func UpdateByIndex[T any](slice []T, index int, value T) []T {
+	size := len(slice)
 
-	if index < 0 || index >= v.Len() {
-		return slice, errors.New("InvalidSliceIndex")
+	if index < 0 || index >= size {
+		return slice
 	}
+	slice = append(slice[:index], append([]T{value}, slice[index+1:]...)...)
 
-	if reflect.TypeOf(slice).Elem() != reflect.TypeOf(value) {
-		return slice, errors.New("InvalidValueType")
-	}
-
-	v.Index(index).Set(reflect.ValueOf(value))
-
-	return v.Interface(), nil
+	return slice
 }
 
 // Unique remove duplicate elements in slice.
@@ -587,24 +566,18 @@ func reverseSlice(slice interface{}) {
 }
 
 // Without creates a slice excluding all given values
-func Without(slice interface{}, values ...interface{}) interface{} {
-	sv := sliceValue(slice)
-	if sv.Len() == 0 {
-		return slice
-	}
-
+func Without[T comparable](slice []T, values ...T) []T {
 	var indexes []int
-	for i := 0; i < sv.Len(); i++ {
-		v := sv.Index(i).Interface()
-		if !Contain(values, v) {
+	for i := 0; i < len(slice); i++ {
+		if !Contain(values, slice[i]) {
 			indexes = append(indexes, i)
 		}
 	}
 
-	res := reflect.MakeSlice(sv.Type(), len(indexes), len(indexes))
-	for i := range indexes {
-		res.Index(i).Set(sv.Index(indexes[i]))
+	res := make([]T, len(indexes), len(indexes))
+	for i, v := range indexes {
+		res[i] = slice[v]
 	}
 
-	return res.Interface()
+	return res
 }
diff --git a/slice/slice_test.go b/slice/slice_test.go
index a252723..9a680b6 100644
--- a/slice/slice_test.go
+++ b/slice/slice_test.go
@@ -263,32 +263,18 @@ func TestInterfaceSlice(t *testing.T) {
 func TestDeleteByIndex(t *testing.T) {
 	assert := internal.NewAssert(t, "TestDeleteByIndex")
 
-	t1 := []string{"a", "b", "c", "d", "e"}
-	r1 := []string{"b", "c", "d", "e"}
-	a1, _ := DeleteByIndex(t1, 0)
-	assert.Equal(r1, a1)
+	assert.Equal([]string{"a", "b", "c"}, DeleteByIndex([]string{"a", "b", "c"}, -1))
+	assert.Equal([]string{"a", "b", "c"}, DeleteByIndex([]string{"a", "b", "c"}, 3))
+	assert.Equal([]string{"b", "c"}, DeleteByIndex([]string{"a", "b", "c"}, 0))
+	assert.Equal([]string{"a", "c"}, DeleteByIndex([]string{"a", "b", "c"}, 1))
+	assert.Equal([]string{"a", "b"}, DeleteByIndex([]string{"a", "b", "c"}, 2))
 
-	t2 := []string{"a", "b", "c", "d", "e"}
-	r2 := []string{"a", "b", "c", "e"}
-	a2, _ := DeleteByIndex(t2, 3)
-	assert.Equal(r2, a2)
-
-	t3 := []string{"a", "b", "c", "d", "e"}
-	r3 := []string{"c", "d", "e"}
-	a3, _ := DeleteByIndex(t3, 0, 2)
-	assert.Equal(r3, a3)
-
-	t4 := []string{"a", "b", "c", "d", "e"}
-	r4 := []string{}
-	a4, _ := DeleteByIndex(t4, 0, 5)
-	assert.Equal(r4, a4)
-
-	t5 := []string{"a", "b", "c", "d", "e"}
-	_, err := DeleteByIndex(t5, 1, 1)
-	assert.IsNotNil(err)
-
-	_, err = DeleteByIndex(t5, 0, 6)
-	assert.IsNotNil(err)
+	assert.Equal([]string{"b", "c"}, DeleteByIndex([]string{"a", "b", "c"}, 0, 1))
+	assert.Equal([]string{"c"}, DeleteByIndex([]string{"a", "b", "c"}, 0, 2))
+	assert.Equal([]string{}, DeleteByIndex([]string{"a", "b", "c"}, 0, 3))
+	assert.Equal([]string{}, DeleteByIndex([]string{"a", "b", "c"}, 0, 4))
+	assert.Equal([]string{"a"}, DeleteByIndex([]string{"a", "b", "c"}, 1, 3))
+	assert.Equal([]string{"a"}, DeleteByIndex([]string{"a", "b", "c"}, 1, 4))
 }
 
 func TestDrop(t *testing.T) {
@@ -311,45 +297,23 @@ func TestDrop(t *testing.T) {
 func TestInsertByIndex(t *testing.T) {
 	assert := internal.NewAssert(t, "TestInsertByIndex")
 
-	t1 := []string{"a", "b", "c"}
-	r1, _ := InsertByIndex(t1, 0, "1")
-	assert.Equal([]string{"1", "a", "b", "c"}, r1)
-
-	r2, _ := InsertByIndex(t1, 1, "1")
-	assert.Equal([]string{"a", "1", "b", "c"}, r2)
-
-	r3, _ := InsertByIndex(t1, 3, "1")
-	assert.Equal([]string{"a", "b", "c", "1"}, r3)
-
-	r4, _ := InsertByIndex(t1, 0, []string{"1", "2", "3"})
-	assert.Equal([]string{"1", "2", "3", "a", "b", "c"}, r4)
-
-	r5, _ := InsertByIndex(t1, 3, []string{"1", "2", "3"})
-	assert.Equal([]string{"a", "b", "c", "1", "2", "3"}, r5)
-
-	_, err := InsertByIndex(t1, 4, "1")
-	assert.IsNotNil(err)
-
-	_, err = InsertByIndex(t1, 0, 1)
-	assert.IsNotNil(err)
+	strs := []string{"a", "b", "c"}
+	assert.Equal([]string{"a", "b", "c"}, InsertByIndex(strs, -1, "1"))
+	assert.Equal([]string{"a", "b", "c"}, InsertByIndex(strs, 4, "1"))
+	assert.Equal([]string{"1", "a", "b", "c"}, InsertByIndex(strs, 0, "1"))
+	assert.Equal([]string{"a", "b", "c", "1"}, InsertByIndex(strs, 3, "1"))
+	assert.Equal([]string{"1", "2", "3", "a", "b", "c"}, InsertByIndex(strs, 0, []string{"1", "2", "3"}))
+	assert.Equal([]string{"a", "b", "c", "1", "2", "3"}, InsertByIndex(strs, 3, []string{"1", "2", "3"}))
+	t.Log(strs)
 }
 
 func TestUpdateByIndex(t *testing.T) {
 	assert := internal.NewAssert(t, "TestUpdateByIndex")
 
-	t1 := []string{"a", "b", "c"}
-	r1, _ := UpdateByIndex(t1, 0, "1")
-	assert.Equal([]string{"1", "b", "c"}, r1)
-
-	t2 := []string{"a", "b", "c"}
-	r2, _ := UpdateByIndex(t2, 1, "1")
-	assert.Equal([]string{"a", "1", "c"}, r2)
-
-	_, err := UpdateByIndex([]string{"a", "b", "c"}, 4, "1")
-	assert.IsNotNil(err)
-
-	_, err = UpdateByIndex([]string{"a", "b", "c"}, 0, 1)
-	assert.IsNotNil(err)
+	assert.Equal([]string{"a", "b", "c"}, UpdateByIndex([]string{"a", "b", "c"}, -1, "1"))
+	assert.Equal([]string{"1", "b", "c"}, UpdateByIndex([]string{"a", "b", "c"}, 0, "1"))
+	assert.Equal([]string{"a", "b", "2"}, UpdateByIndex([]string{"a", "b", "c"}, 2, "2"))
+	assert.Equal([]string{"a", "b", "c"}, UpdateByIndex([]string{"a", "b", "c"}, 3, "2"))
 }
 
 func TestUnique(t *testing.T) {
@@ -418,7 +382,7 @@ func TestDifference(t *testing.T) {
 }
 
 func TestSortByField(t *testing.T) {
-	assert := internal.NewAssert(t, "TestWithout")
+	assert := internal.NewAssert(t, "TestSortByField")
 
 	type student struct {
 		name string