Add square and square root buttons to an existing Javascript calculator built in SL 360

Indeed not to difficult. The square math is already there. Only thing needed was to set the type of calculation on the square button to 's'.
player.SetVar("calculation", "s");

The math for square root wasnot yet present in your code, but luckily Javascript has its own math functionality so using 'Math.sqrt' was easy enough.
mysum = Math.sqrt(mysum);

Setting the calculation to 'r' on the square root button...
player.SetVar("calculation", "r");

As the actual calculation just happens on the '='-button inthere another change needed.
} else if (mycalc == "r") {
mysum = Math.sqrt(mysum);

And thats it. Adding the fixed sample.