How to compute the sum and average of elements in an array?

A solution I consider more elegant:

const sum = times.reduce((a, b) => a + b, 0);
const avg = (sum / times.length) || 0;

console.log(`The sum is: ${sum}. The average is: ${avg}.`);

Calculating average (mean) using reduce and ES6:

const average = list => list.reduce((prev, curr) => prev + curr) / list.length;

const list = [0, 10, 20, 30]
average(list) // 15

ES6

const average = arr => arr.reduce( ( p, c ) => p + c, 0 ) / arr.length;
    
const result = average( [ 4, 4, 5, 6, 6 ] ); // 5
    
console.log(result);

var sum = 0;
for( var i = 0; i < elmt.length; i++ ){
    sum += parseInt( elmt[i], 10 ); //don't forget to add the base
}

var avg = sum/elmt.length;

document.write( "The sum of all the elements is: " + sum + " The average is: " + avg );

Just iterate through the array, since your values are strings, they have to be converted to an integer first. And average is just the sum of values divided by the number of values.