how to add all values in a function 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 numbers in an array javascript

const arrSum = arr => arr.reduce((a,b) => a + b, 0)