find sum of each three numbers in an array in javascript code example

Example 1: sum of all numbers in an array javascript

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

Example 2: sum of two array in javascript

function sumArray(a, b) {
      var c = [];
      for (var i = 0; i < Math.max(a.length, b.length); i++) {
        c.push((a[i] || 0) + (b[i] || 0));
      }
      return c;
}