diff --git a/README.md b/README.md
index 20bc200..29fa3d3 100644
--- a/README.md
+++ b/README.md
@@ -401,7 +401,7 @@ func Drop[T any](slice []T, n int) []T //creates a slice with `n` elements dropp
 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.
-func Find[T any](slice []T, fn func(index int, t T) bool) (*T, bool) //iterates over elements of slice, returning the first one that passes a truth test on function.function signature should be func(index int, value interface{}) bool .
+func Find[T any](slice []T, fn func(index int, t T) bool) (*T, bool) //iterates over elements of slice, returning the first one that passes a truth test on function.function signature should be func(int, T) bool .
 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
diff --git a/README_zh-CN.md b/README_zh-CN.md
index e57739a..49a8914 100644
--- a/README_zh-CN.md
+++ b/README_zh-CN.md
@@ -399,9 +399,9 @@ func ConvertSlice(originalSlice interface{}, newSliceType reflect.Type) interfac
 func Difference[T comparable](slice1, slice2 []T) []T //返回切片，其元素在slice1中，不在slice2中
 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
+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(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(int, T) 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(int, T) bool
 func Filter [T any] (slice []T, fn func(index int, t T) bool) []T //过滤slice
 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
diff --git a/slice/slice.go b/slice/slice.go
index 1b9ad02..41c7dcd 100644
--- a/slice/slice.go
+++ b/slice/slice.go
@@ -72,8 +72,11 @@ func Difference[T comparable](slice1, slice2 []T) []T {
 // Every return true if all of the values in the slice pass the predicate function.
 // The fn function signature should be func(int, T) bool .
 func Every[T any](slice []T, fn func(index int, t T) bool) bool {
-	var currentLength int
+	if fn == nil {
+		panic("fn is missing")
+	}
 
+	var currentLength int
 	for i, v := range slice {
 		if fn(i, v) {
 			currentLength++
@@ -86,8 +89,11 @@ func Every[T any](slice []T, fn func(index int, t T) bool) bool {
 // None return true if all the values in the slice mismatch the criteria
 // The fn function signature should be func(int, T) bool .
 func None[T any](slice []T, fn func(index int, t T) bool) bool {
-	var currentLength int
+	if fn == nil {
+		panic("fn is missing")
+	}
 
+	var currentLength int
 	for i, v := range slice {
 		if !fn(i, v) {
 			currentLength++
@@ -100,6 +106,10 @@ func None[T any](slice []T, fn func(index int, t T) bool) bool {
 // Some return true if any of the values in the list pass the predicate function.
 // The fn function signature should be func(int, T) bool.
 func Some[T any](slice []T, fn func(index int, t T) bool) bool {
+	if fn == nil {
+		panic("fn is missing")
+	}
+
 	for i, v := range slice {
 		if fn(i, v) {
 			return true
@@ -111,6 +121,10 @@ func Some[T any](slice []T, fn func(index int, t T) bool) bool {
 // Filter iterates over elements of slice, returning an slice of all elements `signature` returns truthy for.
 // The fn function signature should be func(int, T) bool.
 func Filter[T any](slice []T, fn func(index int, t T) bool) []T {
+	if fn == nil {
+		panic("fn is missing")
+	}
+
 	res := make([]T, 0, 0)
 	for i, v := range slice {
 		if fn(i, v) {
@@ -121,7 +135,7 @@ func Filter[T any](slice []T, fn func(index int, t T) bool) []T {
 }
 
 // Count iterates over elements of slice, returns a count of all matched elements
-// The function signature should be func(index int, value interface{}) bool .
+// The function signature should be func(int, T) bool .
 func Count[T any](slice []T, fn func(index int, t T) bool) int {
 	if fn == nil {
 		panic("fn is missing")
@@ -142,7 +156,7 @@ func Count[T any](slice []T, fn func(index int, t T) bool) int {
 }
 
 // GroupBy iterate over elements of the slice, each element will be group by criteria, returns two slices
-// The function signature should be func(index int, value interface{}) bool .
+// The function signature should be func(int, value T) bool .
 func GroupBy[T any](slice []T, fn func(index int, t T) bool) ([]T, []T) {
 
 	if fn == nil {
@@ -172,6 +186,10 @@ func GroupBy[T any](slice []T, fn func(index int, t T) bool) ([]T, []T) {
 // The fn function signature should be func(int, T) bool .
 // If return T is nil then no items matched the predicate func
 func Find[T any](slice []T, fn func(index int, t T) bool) (*T, bool) {
+	if fn == nil {
+		panic("fn is missing")
+	}
+
 	if len(slice) == 0 {
 		return nil, false
 	}
@@ -218,6 +236,10 @@ func flattenRecursive(value reflect.Value, result reflect.Value) reflect.Value {
 // ForEach iterates over elements of slice and invokes function for each element
 // The fn function signature should be func(int, T).
 func ForEach[T any](slice []T, fn func(index int, t T)) {
+	if fn == nil {
+		panic("fn is missing")
+	}
+
 	for i, v := range slice {
 		fn(i, v)
 	}
@@ -226,6 +248,10 @@ 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 function signature should be func(int, T).
 func Map[T any, U any](slice []T, fn func(index int, t T) U) []U {
+	if fn == nil {
+		panic("fn is missing")
+	}
+
 	res := make([]U, len(slice), cap(slice))
 	for i, v := range slice {
 		res[i] = fn(i, v)
@@ -237,6 +263,10 @@ func Map[T any, U any](slice []T, fn func(index int, t T) U) []U {
 // Reduce creates an slice of values by running each element of slice thru fn function.
 // The fn function signature should be fn func(int, T) T .
 func Reduce[T any](slice []T, fn func(index int, t1, t2 T) T, initial T) T {
+	if fn == nil {
+		panic("fn is missing")
+	}
+
 	if len(slice) == 0 {
 		return initial
 	}