http://eloquentjavascript.net/06_object.html#p_/6RUkCsOAv

EJS CH6 Exercises

// A Vector Type

function Vector(x, y){
  this.x = x;
  this.y = y;
};

Vector.prototype.plus = function(other_vector) {
  return new Vector(this.x + other_vector.x, this.y + other_vector.y);
};

Vector.prototype.minus = function(other_vector) {
  return new Vector(this.x - other_vector.x, this.y - other_vector.y);
};

Object.defineProperty(Vector.prototype, "length", { get:function() {
  return Math.sqrt(this.x * this.x + this.y * this.y); }
});


console.log(new Vector(1,2));

console.log(new Vector(1, 2).plus(new Vector(2, 3)));
// → Vector{x: 3, y: 5}
console.log(new Vector(1, 2).minus(new Vector(2, 3)));
// → Vector{x: -1, y: -1}
console.log(new Vector(3, 4).length);
// → 5





// Another Cell
function StretchCell(inner, width, height) {
  this.inner = inner;
  this.width = width;
  this.height = height;
}

StretchCell.prototype.minWidth = function() {
  return Math.max(this.inner.minWidth(), this.width);
}

StretchCell.prototype.minHeight = function() {
  return Math.max(this.inner.minHeight(), this.height);
}

StretchCell.prototype.draw = function(width, height) {
  return this.inner.draw(width, height);
}

var sc = new StretchCell(new TextCell("abc"), 1, 2);
console.log(sc.minWidth());
// → 3
console.log(sc.minHeight());
// → 2
console.log(sc.draw(3, 2));
// → ["abc", "   "]





// Sequence Interface

function ArraySeq(array) {
  this.array = array;
  this.pos = -1;
}
Object.defineProperty(ArraySeq.prototype, "continue", { get:function() {
  if (this.pos < this.array.length) {
    this.pos++;
    return true;
  }
  return false;
}});
Object.defineProperty(ArraySeq.prototype, "next", { get:function() {
  return this.array[this.pos];
}});

function RangeSeq(from, to) {
  this.from = from-1;
  this.to = to;
}
Object.defineProperty(RangeSeq.prototype, "continue", { get:function() {
  if (this.from < this.to) {
    this.from++;
    return true;
  }
  return false;
}});
Object.defineProperty(RangeSeq.prototype, "next", { get:function() {
  return this.from;
}});


function logFive(seq) {
  for (var i = 0; i < 5 && seq.continue; i++) {
    console.log(seq.next);
  }
}

logFive(new ArraySeq([1, 2]));
// → 1
// → 2
logFive(new RangeSeq(100, 1000));
// → 100
// → 101
// → 102
// → 103
// → 104