Prime Problem

// Here is a JavaScript code I wrote
// because I originally thought to try 2, 3, and 5 which didn't work
// it tries all a b and c go from 1 to 10 which was enough

function isprime(n) {
    for (var i=2; i<100; ++i) {
        if (n%i===0) {
            if (n !== i) {
                return false;
            }
        }
    }
    if ((n < 2) || ((i%1) !== 0)) {
        return false;
    }
    return true;
};

var t = []; // since javascript allows "everything is a value" I can switch a array to a number
// and it will act as a flag and as the stored value
// don't worry I have no idea what I'm talking about I used to think all the programming
// languages worked the same because how they looked on the surface
// I'm still not a professional or anything

for (var a=2; a<10; ++a) {
    for (var b=2; b<10; ++b) {
        for (var c=2; c<10; ++c) {
            if (isprime(c)) {
                if (t instanceof Array) {
                    if(isprime((a+b+c)/2)) {
                        t = (a+b+c)/2;
                    }
                }
            }
        }
    }
}

console.log(t);
// Post Scriptum I actually wrote this in processing JS on Khan Academy but to make it more
// professional looking I translated it to pure javascript