js如何给对象动态添加属性

请问各位如何动态给对象添加属性？

   var aa = "maker";
    var bb = 1;
    listss = {};
    // listss.a = aa;
    eval("listss."+bb+"="+aa);//missing ;
    eval('('+"listss."+bb+"="+aa+')');//missing ;
    console.log(listss);

---

<script>
    window.onload=function(){
        var person ={};
        person['abc'] = "aasdf";
        alert(person.abc);
    }
</script>


<script>
window.onload=function(){
    var person ={};
    var strArr=["a","b"];
    person['abc'] = "aasdf";
    for (var index = 0; index <= strArr.length; index++) {
        person[strArr[index]]=index;
    }

    for(var item in person)
    {
        document.write(person[item]+"<br>");
    }
}
</script>