[JavaScript] How to combine string and become javascript command

[JavaScript] How to combine string and become javascript command



for (var i=1;i<=6;i++)

{

    var MAC='mac'+i;

    var DateMac='a'+i;

    var b='main_window_a'+i;

    var DocumentValue='document.frm.'+MAC+'.value';

    var DateMac =  eval(DocumentValue);

    window.opener.document.getElementById(b).value = DateMac;  



    if(i != 6)

        MacAddress = MacAddress + DateMac + ':' ;

    else

        MacAddress = MacAddress + DateMac ;

}



Reference:

1. 
   Efficient JavaScript