Call base method in Javascript using Douglas Crockford's functional inheritance

Question

Basically how do I call a base method using this patter below?

var GS = {};
GS.baseClass = function (somedata) {
  var that = {};
  that.data = somedata;

  //Base class method
  that.someMethod = function(somedata) {
    alert(somedata);
  };

  return that;
};

GS.derivedClass = function(somedata) {
 var that = GS.baseClass(somedata);

 //Overwriting base method
 that.someMethod = function(somedata) {
   //How do I call base method from here? 

   //do something else
 };
 return that;
};

Thanks.

Anatoliy · Accepted Answer · 2009-09-23 18:41:52Z

7

var GS = {};
GS.baseClass = function (somedata) {
  var that = {};
  that.data = somedata;

  //Base class method
  that.someMethod = function(somedata) {
    alert(somedata);
  };

  return that;
};

GS.derivedClass = function(somedata) {
 var that = GS.baseClass(somedata);

 //Overwriting base method
 var basemethod = that.someMethod;
 that.someMethod = function(somedata) {
   //How do I call base method from here? 
   basemethod.apply(that, [somedata]);
   //do something else
 };
 return that;
};

Cheers.

answered Sep 23, 2009 at 18:41

Anatoliy

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2 Comments

Sergey Over a year ago

Anatoliy, why do I need to use .apply method in this case? if I can simply call basemethod(somedata)?

Anatoliy Over a year ago

Apply will execute function "basemethod" in context of object "that", i.e. in the method "basemethod" you may use "this" - it will be links to that. If you use basemethod(somedata), function will running in global (window) context, which is incorrect in this case. Sample: <pre> window.myvar = 'window context var'; object = { myvar: 'object context var' }; var fun = function () { alert(this.myvar); } fun(); fun.apply(object); </pre>

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