how to sum values 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: javascript sum array values

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

Example 3: sum function in javascript

let sum = (...para) => para.reduce((d,b) => d + b);