code-201-reading-notes

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Object Literals

What is an object?

Objects group together a set of variables and functions to create a model of a something you would recognize from the real world. In an object, variables and functions take on new names.

• IN AN OBJECT: variables become known as PROPERTIES and functions as METHODS.

Creating an Object: Literal Notation

it is the easiest and most popular way to creat objects as you can see her, dog1 is the object. Name, colors, and age are properties, and “max”, “brown” and “5” are values. if we used a function to return one of these values, we call this function is that case as a method.

• you can access the properties or methods of an object using dot notation, you can also accsess properties using suqare brackets.

The Document Object Model

The Document Object Model (DOM) specifies how browsers should create a model of an HTML page and how JavaScript can access and update the contents of a web page while it is in the browser window. The DOM is neither part of HTML, nor part of JavaScript; it is a separate set of rules. It is implemented by all major browser makers, and covers two primary areas:

• MAKING A MODEL OF THE HTML PAGE: The DOM specifies the way in which the browser should structure this model using a DOM tree. And it’s a model of a web page.

• ACCESSING AND CHANGING THE HTML PAGE: The DOM also defines methods and properties to access and update each object in this model, which in turn updates what the user sees in the browser.

• The browser represents the page using a DOM tree.

• DOM trees have four types of nodes: document nodes, element nodes, attribute nodes, and text nodes.

• You can select element nodes by their id or cl ass attributes, by tag name, or using CSS selector syntax.

• Whenever a DOM query can return more than one node, it will always return a Nadel i st.

• From an element node, you can access and update its content using properties such as textContent and i nnerHTML or using DOM manipulation techniques.

• An element node can contain multiple text nodes and child elements that are siblings of each other.

• In older browsers, implementation of the DOM is inconsistent (and is a popular reason for using jQuery).

• Browsers offer tools for viewing the DOM tree.