A really arcaic calculator for pi, that takes ages to get a little precision.
var ex431 = function(tries){
var inc=0, outc=0, x, y;
while(tries>0){
x = Math.random();
y = Math.random();
if (x*x + y*y <= 1) inc++;
else outc++;
tries--;
}
return inc/(inc+outc);
}for(var i = 0; i<300; i++)
console.log(ex431(100000000)*4);