Question

I want to create a dynamic worksheet for my students, so every time they do it they see different questions. The question that I am trying to create ie, calculate the percentage if I scored X out of a total of Y.

Here are the 3 functions which work together, the first generates some numbers, calls the second, which in turn calls the third to check if it more than 2 decimal places, then if it is, the second creates a new SCORE number which repeats until it finds an answer which is 2 decimal places or less, then returns the SCORE number which works to the first, which outputs it.

I keep getting one of three outputs : undefined where the SCORE should be, no output at all, or a working question.

I cannot understand how it works sometimes, throws undefined sometimes and gives completely nothing at other times.

Any ideas.

function scorePercent()
{
    var output="";
    var total = Math.floor((Math.random()*99)+1);
var score = Math.floor((Math.random()*(total-1))+1);
    output = output + "<div>A score of " + chkScore(score,total) + " out of " + total + ".</div></br>";

    document.getElementById("qOut").innerHTML=output;

}

function chkScore(n1,n2)
{
    var answ = (n1/n2)*100;
    if(dps(answ)>2)
    {
        var scoreNew = Math.floor((Math.random()*(n2-1))+1);
        chkScore(scoreNew, n2);
    }
    else
    {
        return n1;
    }       
}

function dps(num) 
{
    var match = (''+num).match(/(?:\.(\d+))?(?:[eE]([+-]?\d+))?$/);
    if (!match) { return 0; }
    return Math.max(
            0,
        // Number of digits right of decimal point.
            (match[1] ? match[1].length : 0)
        // Adjust for scientific notation.
         - (match[2] ? +match[2] : 0));
}

Answer 1

You have a recursive function in your chkScore, but you’re not return-ing the results from the “deeper” iterations.

Try this:

function chkScore(n1,n2){
    var answ = (n1/n2)*100;
    if(dps(answ)>2) {
        var scoreNew = Math.floor((Math.random()*(n2-1))+1);
        return chkScore(scoreNew, n2); // <-- return that.
    } else {
        return n1;
    }       
}

The missing return there, resulted in the function sometimes not returning anything.

The “deeper” iterations will return their value only 1 “level” up, so that “level” will have to pass it through, if you know what I mean.