how to set the attribute value in javascript code example

Example 1: javascript change attribute

var element = document.getElementById("elemId");
element.setAttribute("attributeName", "value");

Example 2: setAttribute()

element.setAttribute(name, value);
element.setAttribute("style", "background-color: red;");

Example 3: set attribute javascript

Element.setAttribute(name, value);

Example 4: set property dom javascrpt

document.getElementsByTagName("H1")[0].setAttribute("class", "democlass");