javascript - Any way to simplify this code?

Question

New to javascript! This works, but I have a lot more to do, and it would be great if there was a cleaner way to do this.. open to using jquery if neccesary :)

(stack wants me to write more before I submit, though I'm not sure what else to say)

<script>

function apply(){
    var backerPrediction1 = document.getElementById("backer-prediction-1").value;
    var backerPrediction2 = document.getElementById("backer-prediction-2").value;
    var backerPrediction3 = document.getElementById("backer-prediction-3").value;
    var backerPrediction4 = document.getElementById("backer-prediction-4").value;
    var backerPrediction5 = document.getElementById("backer-prediction-5").value;
    var backerPrediction6 = document.getElementById("backer-prediction-6").value;
    var backerPrediction7 = document.getElementById("backer-prediction-7").value;
    var backerPrediction8 = document.getElementById("backer-prediction-8").value;
    var backerPrediction9 = document.getElementById("backer-prediction-9").value;
    var backerPrediction10 = document.getElementById("backer-prediction-10").value;
    var backerPrediction11 = document.getElementById("backer-prediction-11").value;
    var backerPrediction12= document.getElementById("backer-prediction-12").value;
    var backerPrediction13 = document.getElementById("backer-prediction-13").value;
    var backerPrediction14 = document.getElementById("backer-prediction-14").value;
    var backerPrediction15 = document.getElementById("backer-prediction-15").value;
    var backerPrediction16 = document.getElementById("backer-prediction-16").value;
    var backerPrediction17 = document.getElementById("backer-prediction-17").value;
    var backerPrediction18 = document.getElementById("backer-prediction-18").value;
    var backerPrediction19 = document.getElementById("backer-prediction-19").value;
    var backers = parseInt(backerPrediction1,10) +
              parseInt(backerPrediction2,10) +
              parseInt(backerPrediction3,10) +
              parseInt(backerPrediction4,10) +
              parseInt(backerPrediction5,10) +
              parseInt(backerPrediction6,10) +
              parseInt(backerPrediction7,10) +
              parseInt(backerPrediction8,10) +
              parseInt(backerPrediction9,10) +
              parseInt(backerPrediction10,10) +
              parseInt(backerPrediction11,10) +
              parseInt(backerPrediction12,10) +
              parseInt(backerPrediction13,10) +
              parseInt(backerPrediction14,10) +
              parseInt(backerPrediction15,10) +
              parseInt(backerPrediction16,10) +
              parseInt(backerPrediction17,10) +
              parseInt(backerPrediction18,10) +
              parseInt(backerPrediction19,10)
;
document.getElementById("backer-prediction-answer").value = (backers);
}
</script>

Thanks for your help!! :)

Answer 1

I'd do it something like this:

function apply() {
    var backers = 0;
    for (var i = 1; i < 20; ++i) {
        backers +=
            parseInt(document.getElementById("backer-prediction-" + i).value);
    }
    document.getElementById("backer-prediction-answer").value = backers;
}