how to get the value from a select box in javascript code example

Example 1: javascript get selected option

var e = document.getElementById("selectElementID");
var value=e.selectElement.options[e.selectedIndex].value;// get selected option value
var text=e.options[e.selectedIndex].text;//get the selected option text

Example 2: get selection value javascript

var e = document.getElementById("ddlViewBy");
var strUser = e.value;