add class in javascript to get element by tag inside code example

Example 1: get elment by id within get element byclassname

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

Example 2: javascript get all elements of an id

// You can't
// You can only have 1 instance of an id per document
// You need to use classes instead

var x = document.getElementsByClassName("example");