Question

I don’t understand how ‘s’ is being used in ‘(+s[i])’. What is the ‘+’ for? Also I do not understand the use of the || symbol in this way, what is it doing?

var draw = function(s){
...
if (+s[i]) a = (a+90)%360||360; // Right
else a = (a-90||360); // Left

In the code below I do not understand what ‘while (n–)’ does?

var getS = function(n){
    var s = '';
    while (n--) s += getNext(0);
    return s;
};

If you want to look at this code in context go to http://fractal.qfox.nl/ and press F12 to get the developer tools up and look for dragon.js in the scripts. Please feel entirely free to post a complete translation to C# as well if you fancy the challenge.

Answer 1

Putting + in front of an expression coerces it into a number, e.g. from a string.

The || operator has the value of its left side if that can convert to true, otherwise the value of its right side. And so a||b would mean “use a if it’s not null, false, zero or an empty string, otherwise use b”.

And n-- will have boolean value false when n reaches zero.