Vector.js

define(['vendor/lodash'],function(){
  "use strict";

  function Vector(x,y) {
    this.x = x || 0;
    this.y = y || 0;
  }

  _.extend(Vector.prototype, {
    getMagnitude : function() {
      return Math.sqrt(this.x * this.x + this.y * this.y);
    },
    multiply : function( scaleFactor ){
      this.x *= scaleFactor;
      this.y *= scaleFactor;
    },
    add : function( vector ){
      this.x += vector.x;
      this.y += vector.y;
    },
    vectorTo : function (vector) {
      return new Vector(vector.x - this.x, vector.y - this.y);
    },
    withinBounds : function(point, size) {
      var radius = ~~(size/2)  + 1;
      return this.x >= point.x - radius &&
             this.x <= point.x + radius &&
             this.y >= point.y - radius &&
             this.y <= point.y + radius ;
    },
    getAngle : function() {
      var ratio = 0;
      var offset = 0;
      if (this.x > 0) {
        if (this.y > 0) {
          offset = 0;
          ratio = this.y / this.x;
        } else {
          offset = (3 * Math.PI)/2;
          ratio = this.x / this.y;
        }
      } else {
        if (this.y > 0) {
          offset = Math.PI / 2;
          ratio = this.x / this.y;
        } else {
          offset = Math.PI;
          ratio = this.y / this.x;
        }
      }
      var angle = Math.atan(Math.abs(ratio)) + offset;
      return angle;
    },
    getAngleDegrees : function() {
      return this.getAngle() * 180 / Math.PI;
    },
    jitter : function(jitterAmount) {
      return new Vector(
        this.x + this.x * jitterAmount * Math.random(),
        this.y + this.y * jitterAmount * Math.random()
      );
    },
    copy : function() {
      return new Vector(this.x,this.y);
    },
    toString : function() {
      return this.x.toFixed(3).replace(/\.?0+$/,'') +","+ this.y.toFixed(3).replace(/\.?0+$/,'');
    }
  });

  Vector.fromAngle = function (angle, magnitude) {
    return new Vector(magnitude * Math.cos(angle), magnitude * Math.sin(angle));
  };

  // x,y
  Vector.fromString = function (string) {
    var parts = string.split(',');
    return new Vector(parseFloat(parts[0]),parseFloat(parts[1]));
  };

  return Vector;
});