Javascript Object Inheritance - Extend and Multiple

These two javascript functions does the inheritance

//inheritance
function extendCopy(obj){
    var n = {};
    for(var i in obj){
        n[i] = obj[i];
    }
    n.uber = obj;
    return n;
}

//multiple inheritance
function multi(){
    var n={}, stuff, j=0, len = arguments.length;
    for(j=0;j<len;j++){
        stuff = arguments[j];
        for(var i in stuff){
            n[i] = stuff[i]; 
        }
    }
    return n;
}

Below test the object to see if it worked

//Setting objections
var first_obj = {name:'first', doSomething: function(){alert(2+2);}}
var second_obj = {date:'today', location: 'USA'}
var third_obj = {felling:'happiness', status: 'fun'}
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//append/inheritance first first_obj to second_obj
var second_obj = extendCopy(first_obj);
document.write(second_obj.name); // first

//add both the first_obj and third_obj at the same time
var fourth_obj = multi(first_obj,third_obj);
document.write(fourth_obj.felling);// happiness

Another example of javascript inheritance using constructors