sum last 9 elements in map javascript code example

Example 1: add all elements in array javascript

console.log(
  [1, 2, 3, 4].reduce((a, b) => a + b, 0)
)
console.log(
  [].reduce((a, b) => a + b, 0)
)

Example 2: sum of all elements in array javascript

arrSum = function(arr){  return arr.reduce(function(a,b){    return a + b  }, 0);}