The browser exposes `window` as the global object representing the window containing a page. JavaScript uses it to access global objects, variables, and browser APIs; its `document` property represents the page’s DOM. section 2.2.2
Accessing the page
Use `document.getElementById("first")` to select an element, then JavaScript can change its content or attributes, add children, or remove it. section 2.2.2
var first = document.getElementById("first");
See the element-selection example using the global `document` object. section 2.2.2
