adding numbers in an array javascript

const sum = arr => arr.reduce((a, b) => a + b, 0);const arrSum = arr => arr.reduce((a,b) => a + b, 0)arrSum = function(arr){  return arr.reduce(function(a,b){    return a + b  }, 0);}console.log(
  [].reduce((a, b) => a + b)
)