reading-notes

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THE OBJECT

• Object is the basic building unit of the program.

  “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.”(PROPERTIES , METHODS)

• If we need to use a variable as part of an object, called a property, It tell us information about the object.
• a method is a function when be part of an object, It is the tasks that are associated with the object.
• properties and methods have a name and a va lue. The name is called a key.
• You cannot put two keys with the same name.

• The value of a method is always a function.

• 
  • Almost “everything” can be an object :
    • Booleans can be objects (with the new keyword)
    • Numbers can be objects (with the new keyword)
    • Strings can be objects (with the new keyword)
    • Dates are always objects
    • Maths are always objects
    • Regular expressions are always objects
    • Arrays are always objects
    • Functions are always objects
    • Objects are always objects
• Literal notation is the most popular way to create objects.

Accessing an object and dot notation

• The content of the page is updated with data from this object.
• To access a property of this object, the object name is followed by a dot (the period symbol) and the name of the property that you want.
• Similarly, to use the method, you can use the object name followed by the method name.

Document Object Model (DOM)

• “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.”

DOM tree

• a tree structure wherein each node is an object representing a part of the document.
• 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.

  Application Programming Interface (API)

• let programs (and scripts) talk to each other.
• A Web API is an application programming interface for the Web.
• A Browser API can extend the functionality of a web browser.
• A Server API can extend the functionality of a web server.
• ELEMENT NODES , describe the structure of an HTML page.
• “Each node is an object with methods and properties.”
• Whenever a DOM query can return more than one node, it will always return a Nadel i st.

DOM tree steps:

1. Locate the node that represents the element you want to work with.
2. Use its text content, child elements, and attributes.
   • Can return one element, or they may return a Nodelist, we may use id (or any) for Customizable.

     

   • Node-list is a type of object called a collection.
     • Nodelists have a method called item(), they return an individual node
   • we can use sentences like: for , if … in it.
   • 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).