how to change id of element in javascript code example

Example 1: javascript change element id

var element = document.getElementById("oldID");
element.id = "newID";

Example 2: get id of element javascript

var element = document.getElementsByTagName("div")[0];
var id = element.id;

Example 3: js get id value

var element = document.getElementById("YourElementId");
var value_element = document.getElementById("YourElementId").value;