What Is A Function?

• Functions let you group a series of statements together to perform a specific task.
• If different parts of a script repeat the same task, you can reuse the function.

Declaring A Function

• To create a function, you give it name and then write the statements needed to achieve its task inside the curly braces.
• This is known as a function declaration.

Calling A Function

• Having declared the function, you can then execute all of the statements between its curly braces with just one line of code.
• Thins is known as calling the function.

Declaring Functions That Need Information

• Sometimes a function needs specific information to perform its task.
• In such cases, when you declare the function you give it parameters.
• Inside the function, the parameters act like variables.

Calling Functions That Need Information

• When you call a function that has parameters, you specify the values it should use in the parentheses that follow its name.
• The values are called arguments, and they can be provided as values or as variables.

Getting A Single Value Out Of A Function

• Some functions return information to the code that called them.
• For example, when they perform a calculationl, they return the result.

Getting Multiple Values Out Of A Function

• Functions can return more than one value using an array.
• For example, the function calculates the area and volume of a box.

What Is An Object?

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

IN AN OBJECT: VARIALBLES BECOME KNOWN AS PROPERTIES

• If a variable is part of an object, it is called a property.
• Properties tell us about the object, such as the name of a hotel or the number of rooms it has.

IN AN OBJECT: FUNCTIONS BECOME KNOWN AS METHODS

• If a function is part of an object, it is called a method.
• Methods represent tasks that are associated with the object.

Adding AND Removing Properties

• Once you have created an object, you can add new properties to it.
• You do this using the dot notation.
• Ex. hotel.gym = true; hotel.pool = false
• To delete a property, you use the keyword delete, and then use dot notation to identify the property or method you want to remove from the object.
• Ex. delete.hotel.booked

This

• The keyword this is commonly used inside functions and objects.
• Where the function is declared alters what this means.
• It always refer to one object, usually the object in which the function operates.

Arrays And Objects

• Arrays are actually a special type of object.
• They hold a related set of key and value pairs, but the key for each value is its index number.
• You can combine arrays and objects to create complex data structures.
• Arrays can store a series of objects and remember their orders.
• Objects can also hold arrays as value of their properties.

What Are Built-In Objects

• Browsers come with a set of built-in objects that represent things like the browser window and the current web page shown in that window.
• These built-in objects act like a toolkit for creating interactive web pages.
  • Browser Object Model
  • Document Object Model
  • Global JavaScript Objects