javascript - js array accumulation problem

Question

val is a parameter, and a value is passed every time you click, but the array does not accumulate. I don’t know why.

Answer 1

Because the array you accumulate is new every time, arr is reassigned to ['s', 'd'] every time.

Answer 2

Just define var arr = [] outside the current function, similar to this:

var arr = ['s', 'd']

function addArr(val){
    arr.push(val)
}