Javascript inheritance using prototype, what is the practical way?

I was reading about inheritance in Javascript and came up with creating constructors and defining each constructor prototype. I created a function prototypeExtend

that will loop through each constructor prototype and add it to the main constructor prototypes.

Is this a practical way to achieve inheritance?

function prototypeExtend() {
    var cMain = arguments[0].prototype;
    for(var i=1; i<arguments.length; i++){
        var cTemp = arguments[i].prototype;
        for(var k in cTemp){
            if(cTemp.hasOwnProperty(k)){
                cMain[k] = cTemp[k];
            }
        }
    }
    return cMain;
}

function Class1 () {}
Class1.prototype = {
        el1:null,
        fun1:function(str){
            console.log(str + " from Class1");
        },
        setEl1:function(value){
            this.el1 = value;
        },
        getEl1:function(){
            return this.el1;
        }
}

function Class2(){}
Class2.prototype = {
        el2:"blah",
        fun2:function(str){
            console.log(str + " from Class2");
        }
}

function Class3(){}
Class3.prototype = {
        el3:"dah",
        fun3:function(str){
            console.log(str + " from Class3");
        },
        fun1:function(str){
            console.log(str + " from Class3");
        }
}
prototypeExtend(Class2, Class1, Class3);
var obj = new Class2;
console.log(obj);