get element by class and id code example

Example 1: javascript get element by class

var elementsArray = document.getElementsByClassName("someclassname");

Example 2: javascript get element by class

var elements = document.querySelector(".class");

Example 3: get elment by id within get element byclassname

var targetDiv = document.getElementById("foo").getElementsByClassName("bar")[0];
targetDiv.textContent = "Goodbye world!";