finding sum in javascript without sum function, reduce code example

Example 1: sum of number using reduce

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

Example 2: javascript reduce sum

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