# 30秒学会 Golang 片段 – FindIndex

Returns the index of the first element in the provided collection that satisfies the provided testing function, `-1` otherwise.

Implement an appropriate function for each type.
Use `range` to iterate over elements in the given collection, using `f` to determine if the element matches.
Return the index of the first matching element or `-1` if none is found.

#### 代码实现

``````func FindIndexInt(arr []int, f func(int) bool) int {
for i, v := range arr {
if f(v) {
return i
}
}
return -1
}
func FindIndexFloat64(arr []float64, f func(float64) bool) int {
for i, v := range arr {
if f(v) {
return i
}
}
return -1
}
func FindIndexBool(arr []bool, f func(bool) bool) int {
for i, v := range arr {
if f(v) {
return i
}
}
return -1
}
func FindIndexString(arr []string, f func(string) bool) int {
for i, v := range arr {
if f(v) {
return i
}
}
return -1
}``````

#### 使用样例

``````FindIndexInt([]int{1, 1, 2}, func(x int) bool { return x%2 == 0 }) // 2
FindIndexFloat64([]float64{4.0, 6.0}, func(x float64) bool { return x%2.0 == 1.0 }) // -1``````