javascript的接口定义之鸭式辨型

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<!DOCTYPE HTML>  <html>      <head>          <script type="text/javascript">              var Interface = function(name, methods){                  if(arguments.length != 2){                      throw new Error('Interface constructor called with ' + arguments.length                          + 'arguments, but expected exactly 2.');                  }                                    this.name = name;                  this.methods = [];                  for(var i=0,len = methods.length; i<len; i++){                      if(typeof methods[i] != 'string'){                          throw new Error('Interface constructor expected method names to be '                              + 'passed in as a string.');                      }                      this.methods.push(methods[i]);                  }              };                            Interface.ensureImplements = function(object){                  if(arguments.length < 2){                      throw new Error("Function Interface.ensureImplements called with " + arguments.length                           + " arguments, but expected at least 2.");                  }                                    for(var i=1,len = arguments.length; i < len; i++){                      var interface = arguments[i];                      if(interface.constructor != Interface){                          throw new Error("Function Interface.ensureImplements expects arguments "                              + "two and above to be instances of Interface.");                      }                                            for(var j=0,methodslen = interface.methods.length; j < methodslen; j++){                          var method = interface.methods[j];                          if(!object[method] || typeof object[method] !== 'function'){                                throw new Error("Function Interface.ensureImplements: object " +                                    "does not implements the " + interface.name + " interface.Method " +                                   method + " was not found.");                            }                      }                  }              };                            // 定义接口              var DynamicMap = new Interface('DynamicMap', ['centerOnPoint', 'zoom', 'draw']);                            function displayRoute(mapInstance){                  // 接口实现检查                  Interface.ensureImplements(mapInstance, DynamicMap);                                    mapInstance.centerOnPoint(24, 13);                  mapInstance.zoom(5);                  mapInstance.draw();              }                            // 对象              function Foo(){              }                            Foo.prototype = {                  centerOnPoint : function(x, y){                      document.writeln('<br />centerOnPoint: ' + x + ', ' + y);                  },                  zoom : function(level){                      document.writeln('<br />zoom: ' + level);                  },                  draw : function(){                      document.writeln('<br />draw');                  }              };                            var foo = new Foo();              displayRoute(foo);                        </script>      </head>  </html>
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