Can I do this in JavaScript? Conditional return if arguments not passed

Question

I want to be able to pass this function either a number to return as a factorial or a number and an id for an existing element on the page, so that it can return the number as text inside my specified element. Here is my code:

function factorial(num,id){
    var f=1
    for (var i=2; i<=num; i++) {
        f*=i;
    }
    if (!id) {
        return f;
    }
    else if (id) 
        var msg= document.getElementById(id);
        return {
        msg.textContent = num + "! =  " + output;
        };
    }
}

factorial(5,"message");

why not return num + "! = " + output; where does output come from ? — Konstantin Krass
– Konstantin Krass, Commented Jul 2, 2014 at 14:09

Alex K. · Accepted Answer · 2014-07-02 14:13:26Z

1

Set the element if passed then return unconditionally:

function factorial(num, id){
    var f = 1;
    for (var i=2; i<=num; i++) {
        f *= i;
    }

    if (id) {
        document.getElementById(id).textContent = num + "! =  " + f;
    }

    return f;
 }

alert(factorial(5));

alert(factorial(5,"message"));

answered Jul 2, 2014 at 14:13

Alex K.

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3 Comments

Eric Bishard Over a year ago

Ahh I see what I was doing wrong. Plus I had used output without defining it. This works better.

Alex K. Over a year ago

Also for IE7/8 you need .innerText rather than .textContent. In this case you can use .innerHTML which works in everything

Eric Bishard Over a year ago

Thank for the tip. I knew innerHTML was good all around but wasn't aware that ie 7/8 wouldn't work with .textContent. Thanks for the heads up!

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