probability in javascript help?

Question

Sorry, I\'m new to JS and can\'t seem to figure this out: how would I do probability?

I have absolutely no idea, but I\'d like to do something: out of 100% chance, m

Answer 1

For instance we define a number of functions

function a () { return 0; }
function b () { return 1; }
function c () { return 2; }

var probas = [ 20, 70, 10 ]; // 20%, 70% and 10%
var funcs = [ a, b, c ]; // the functions array

That generic function works for any number of functions, it executes it and return the result:

function randexec()
{
  var ar = [];
  var i,sum = 0;


  // that following initialization loop could be done only once above that
  // randexec() function, we let it here for clarity

  for (i=0 ; i=ar[i] ; i++) ;

  // Finally execute the function and return its result

  return (funcs[i])();
}

For instance, let's try with our 3 functions, 100000 tries:

var count = [ 0, 0, 0 ];

for (var i=0 ; i<100000 ; i++)
{
  count[randexec()]++;
}

var s = '';
var f = [ "a", "b", "c" ];

for (var i=0 ; i<3 ; i++)
  s += (s ? ', ':'') + f[i] + ' = ' + count[i];

alert(s);

The result on my Firefox

a = 20039, b = 70055, c = 9906

So a run about 20%, b ~ 70% and c ~ 10%.

Edit following comments.

If your browser has a cough with return (funcs[i])();, just replace the funcs array

var funcs = [ a, b, c ]; // the old functions array

with this new one (strings)

var funcs = [ "a", "b", "c" ]; // the new functions array

then replace the final line of the function randexec()

return (funcs[i])(); // old

with that new one

return eval(funcs[i]+'()');