how to set value to select tag in javascript code example

Example 1: html get selected option javascript

<select id="ddlViewBy">
  <option value="1">test1</option>
  <option value="2" selected="selected">test2</option>
  <option value="3">test3</option>
</select>

<script>
    var e = document.getElementById("ddlViewBy");
	var strUser = e.value; // 2
	var strUser = e.options[e.selectedIndex].text; //test2
</script>

Example 2: javascript set html select value

// Get the html select element
var select = document.getElementById('<your select element id>');

// If you have a <option> like this:
// <option value="1">My Value Display text</option>

//Then your selected value of your select would be:

select.value = "1";