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}.`);

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.

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);