How to insert element at the beginning of a slice?

Question

I have a slice:

mySlice := []int{4,5,6,7}
myelement := 3

I want to insert myelement at index 0 so that my output will be [3,4,5,6,7].

How can I do that?

Answer 1

you can use the append property here.

first, need to make a slice with the myelement. then append the slice in mySlice

mySlice = append(myelement, mySlice...)

this is the function that will return the myelement inserting in the first place of the slice.

func addElementToFirstIndex(x []int, y int) []int {
    x = append([]int{y}, x...)
    return x
}

See

Answer 2

func addFirst(s []int, insertValue int) []int {
   res := make([]int, len(s)+1)
   copy(res[1:], s)
   res[0] = insertValue
   return res
}

Another solution, former answers are better.