javascript sum array values

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

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

// Output: 10

function getArraySum(a){
    var total=0;
    for(var i in a) { 
        total += a[i];
    }
    return total;
}

var payChecks = [123,155,134, 205, 105]; 
var weeklyPay= getArraySum(payChecks); //sums up to 722

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

array.reduce((a, b) => a + b, 0)