for (..of..), getters and setters now added to Espruino

I've just added the following to cutting-edge Espruino builds. These will be shipped in Espruino releases 1v100 and later (1v99 doesn't have them):

for (..of..)

This is a nice way of iterating over array/object properties, and will support iterators in the future. It's a more sane version of for (..in..) that returns values not keys, and that doesn't iterate over inherited properties.

>var arr = ["One", "Two", "Three"];
=[ 
  "One", 
  "Two", 
  "Three"
 ]
>for (var i of arr) console.log(i)
One
Two
Three

Getters and setters

You can now call a function when a value is read or written in an object. These work in normal object definitions:

>var foo = {
:  set contents(x) { this._contents = x; },
:  get sum() { 
:    var s=0;
:    for (var i of this._contents) s+=i;
:    return s;
:  }
:};
={  }
>foo.contents = [1,2,3,4];
=undefined
>foo.sum
=10

Using the old defineProperty way:

>var o = {a: 41};
={ "a": 41 }
>Object.defineProperty(o, 'b', { get: function() { return this.a + 1; } });
={ "a": 41 }
>o.b
=42

Or even inside the new classes:

>class Example {
:  get hello() {
:    return 'world';
:  }
:}
=function () {}
>const obj = new Example();
=Example: {  }
>obj.hello
="world"