how to change attributes using java script code example

Example 1: javascript set attribute href

var a = document.getElementById('myElementID');
    a.href = "http://www.mywebsite.com";

Example 2: javascript setattribute

element.setAttribute(<name>, <value>);
// ex
var aElement = document.querySelector("a"); 
aElement.setAttribute("href", "https://isitchristmas.com/"); 
// same as <a href="https://isitchristmas.com/"></a>