4. JS 디자인 모델과 개발 실천 발췌(二)

// 
var CreateDiv = function( html ){
  this.html = html;
  this.init();
};
CreateDiv.prototype.init = function(){
  var div = document.createElement( 'div' );
  div.innerHTML = this.html;
  document.body.appendChild( div );
};

// proxySingletonCreateDiv：
var ProxySingletonCreateDiv = (function(){
  var instance;
  return function( html ){
    if ( !instance ){
       instance = new CreateDiv( html );
    }
    return instance;
   }
})();
var a = new ProxySingletonCreateDiv( 'sven1' );
var b = new ProxySingletonCreateDiv( 'sven2' );
alert ( a === b );

var MyApp = {
  event: {},
  dom: {
    style: {}
  }
};

//  ， ：
var user = (function(){
   var __name = 'sven',
   __age = 29;
   return {
     getUserInfo: function(){
       return __name + '-' + __age;
     }
   }
})();
// __name  __age， ， ， 。

//  ， getSingle ， fn  getSingle  
var getSingle = function( fn ){
  var result;
  return function(){
     return result || ( result = fn .apply(this, arguments ) );
   }
};
//  
var createLoginLayer = function(){
  var div = document.createElement( 'div' );
  div.innerHTML = ' ';
  div.style.display = 'none';
  document.body.appendChild( div );
  return div;
};
var createSingleLoginLayer = getSingle( createLoginLayer );
document.getElementById( 'loginBtn' ).onclick = function(){
  var loginLayer = createSingleLoginLayer();
  loginLayer.style.display = 'block';
};