Personally I would use an inline if statement, as the other methods could potentially give you a -1 as your number.
You could even make it a function of the boolean object (but this is sort of overkill):
code:
Boolean.prototype.toInt = function () { return this ? 1 : 0; }
// to use it, just call the toInt member of a boolean object
function doSomethingWithBooleans() {
var bMyBoolean = true;
var nBoolAsInteger = bMyBoolean.toInt();
}