The anatomy of a plugin

// Define a new method called initialize on Window_MyWindow.prototype
Window_MyWindow.prototype.initialize = function(x, y, width, height) {
  // Create a new Rectangle object with the given x, y, width and height parameters
  var rect = new Rectangle(x, y, width, height);
  // Call the initialize method of Window_Base with this object and the rect object as arguments
  Window_Base.prototype.initialize.call(this, rect);
  // Call the refresh method of this object
  //this.refresh(); //commented to try the update method instead so anything within is updated in realtime
};

/*:
 * @target MZ
 * @plugindesc Testing plugins.
 * @author holymotherofchristsendhelp
*/

// Define a new function called Window_MyWindow
function Window_MyWindow() {
  // Call the initialize method of this function with the given arguments
  this.initialize.apply(this, arguments);
}

// Set the prototype of Window_MyWindow to be an object that inherits from Window_Base
Window_MyWindow.prototype = Object.create(Window_Base.prototype);
// Set the constructor property of Window_MyWindow.prototype to be Window_MyWindow
Window_MyWindow.prototype.constructor = Window_MyWindow;

// Define a new method called initialize on Window_MyWindow.prototype
Window_MyWindow.prototype.initialize = function(x, y, width, height) {
  // Create a new Rectangle object with the given x, y, width and height parameters
  var rect = new Rectangle(x, y, width, height);
  // Call the initialize method of Window_Base with this object and the rect object as arguments
  Window_Base.prototype.initialize.call(this, rect);
  // Call the refresh method of this object
  this.refresh();
};

var textDrawn = false;
// Define a new method called refresh on Window_MyWindow.prototype
Window_MyWindow.prototype.refresh = function() {
  // Draw the amount of gold that the party has at coordinates (0, 0) with a width equal to the window contents width and a height equal to one line of text
  if(textDrawn == true){
    console.log("Text is already drawn")
    //this.clear(); // Doesn't work...
    this.drawText($gameParty.gold(), 0, 0, this.contentsWidth(), this.lineHeight()); // Gold as an example of something I can easily update and see reflected in the box
  }else{
    console.log("First time drawing text")
    this.drawText($gameParty.gold(), 0, 0, this.contentsWidth(), this.lineHeight()); // Gold as an example of something I can easily update and see reflected in the box
    textDrawn = true;
  }
};

// Store the original createAllWindows method of Scene_Map.prototype in a variable
var _Scene_Map_createAllWindows = Scene_Map.prototype.createAllWindows;
// Overwrite the createAllWindows method of Scene_Map.prototype with a new function
Scene_Map.prototype.createAllWindows = function() {
  // Call the original createAllWindows method with this object as argument
  _Scene_Map_createAllWindows.call(this);
  // Call the createMinimapWindow method of this object only once
  if (!this._minimapCreated) {
    this.createMinimapWindow();
    this._minimapCreated = true; // Set a flag so I don't call it again
    console.log("I was called");
  }
};

// Define a new method called createMinimapWindow on Scene_Map.prototype
Scene_Map.prototype.createMinimapWindow = function() {
  // Create a new instance of Window_MyWindow with some parameters for x, y, width and height
  this.myWindow = new Window_MyWindow(0, 0, 200, 200);
  // Add the myWindow object to the children array of this object
  this.addChild(this.myWindow);
};

// Store the original update method of Scene_Map.prototype in a variable
var _Scene_Map_update = Scene_Map.prototype.update;
// Overwrite the update method of Scene_Map.prototype with a new function
Scene_Map.prototype.update = function() {
  // Call the original update method with this object as argument
  _Scene_Map_update.call(this);
  // Call the refresh method on the instance of Window_MyWindow
  this.myWindow.refresh();
};