javascriptはいくつかの方法を継承します.

var m1 = function(){};  
var m2 = function(){};  

1>Object.extend( m1.prototype, m2.prototype );  
2>m1.prototype = m2.prototype;  
3>m1.prototype = new m2();  
4>function m1(cfg) {
    m2.call(this,cfg);
}