inheritance - How to invoke method which rewrite in sub class using javascript(es5) -

i hava 2 class, 1 base class called chartbase, other sub class called chartextend, code following:

/*base class defined*/ function chartbase(element, data, settings, type) {   //   this.init(); }; chartbase.prototype = {   init:function(){     this.initconfig();     // other things;   },   initconfig:function(){     this.setbaseconfig();   },   setbaseconfig:function(){     // something;   } }  /*sub class defined*/ function chartextend(element, data, settings, type) {    chartbase.apply(this, arguments); }; chartextend.prototype = {   initconfig:function(){     this.setbaseconfig();     this.setexternalconfig();   },   setexternalconfig:function(){     // something;   } };  /*sub class extend base class*/ var tempclass = function() {};　　 tempclass.prototype = chartbase.prototype;　　 chartextend.prototype = new tempclass();　 chartextend.prototype.constructor = chartextend; chartextend.uber = chartbase.prototype;  /*instance*/ new chartextend(selector, data, settings, 'line'); 

i found 'initconfig' method invoked in chartbase, not method in chartextend when created instance, however, 'this' pointed chartextend in 'init' function.

1. why still call own prototype method in chartbase?

2. how invoke rewrited method in chartextend?

first of all, overwriting methods defined in chartextend.prototype when doing chartextend.prototype = new tempclass();. that's why, when invoke initconfig method, of chartbase , not of chartextend.

to correct this, need inherit classes base class methods can overridden sub class method. see below example.

// base class  function chartbase() {}    // prototype functions  chartbase.prototype.initconfig = function() {    console.log('base class :: initconfig');  }  chartbase.prototype.setbaseconfig = function() {    console.log('base class :: setbaseconfig');  }    // sub class  function chartextent() {    chartbase.apply(this, arguments);  }    // extend base class  chartextent.prototype = new chartbase()    // define sub class prototypes  chartbase.prototype.initconfig = function() {    console.log('sub class :: initconfig');    this.setbaseconfig();  }    // create instance   var instance = new chartextent()    // call instance method  instance.initconfig()