can somebody help me understand this more. javascript selection : 
var select = document.getElementById('select');

var opsArray= select.options;




select.onchange = userSelection;


function userSelection(){
    
var i = select.selectedIndex;
    
    document.location.assign('projects/' + opsArray[i].value + '/');
    
}



so i know that when the user select the page they want it will go there. what i want is for somebody to enplane this to me, this is the part of JavaScript that i am confused with. so if i just had a block menu instead of a select menu, how will this code go with that. well basically how do that "userSlection/opsArray[i].value" work......i know how to do this in html ""folder/aboutpage/this.index"". but how do that code above work?? thanks in avances.