201-reading-notes

this is where i keep my 201 notes

CLASS 04 READING NOTES

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Key Concepts in positioning eLements

Building Blocks CSS treats each HTML element as if it is in its own box. This box will either be a block-level box or an inline box.
Containing Elements If one block-level element sits inside another block-level element then the outer box is known as the containing or parent element.
Controlling the position of elements CSS has the following positioning schemes that allow you to control the layout of a page: normal flow, relative positioning, and absolute positioning. You specify the positioning scheme using the position property in CSS. You can also float elements using the float property.
Screen Sizes Different visitors to your site will have different sized screens that show different amounts of information, so your design needs to be able to work on a range of different sized screens.
Screen Resolution Resolution refers to the number of dots a screen shows per inch. Some devices have a higher resolution than desktop computers and most operating systems allow users to adjust the resolution of their screens.

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 (rather than repeating the same set of statements). Grouping together the The steps that the function On the right, there is an example statements that are required to needs to perform in order to of a function in the JavaScript answer a question or perform a perform its task are packaged file. It is called updateMessage (). task helps organize your code. up in a code block. The statements in a that a code block consists of one understand the syntax of the function are not always executed or more statements contained example on the right; you will when a page loads, so functions within curly braces. (And you do take a closer look at how to write also offer a way to store the steps not write a semicolon after the and use functions in the pages needed to achieve a task. The closing curly brace - like you do that follow. script can then ask the function after a statement.) to perform all of those steps as Remember that programming and when they are required. Some functions need to be languages often rely upon on For example, you might have provided with information in name/value pairs. The function a task that you only want to order to achieve a given task. For has a name, updateMessage, perform if the user clicks on a example, a function to calculate and the value is the code block specific element in the page. the area of a box would need (which consists of statements). to know its width and height. When you call the function by its If you are going to ask the Pieces of information passed name, those statements will run. function to perform its task to a function are known as later, you need to give your parameters. You can also have anonymous function a name. That name functions. They do not have a should describe the task it is When you write a function and name, so they cannot be called. performing. When you ask it to you expect it to provide you Instead, they are executed as perform its task, it is known as with an answer, the response is soon as the interpreter comes calling the function. known as a return value. across them.

ANONYMOUS FUNCTIONS & FUNCTION EXPRESSIONS

Expressions produce a value. They can be used where values are expected. If a function is placed where a browser expects to see an expression, (e.g., as an argument to a function), then it gets treated as an expression.

FUNCTION DECLARATION A function declaration creates a function that you can call later in your code.
FUNCTION EXPRESSION If you put a function where the interpreter would expect to see an expression, then it is treated as an expression, and it is known as a function expression. In function expressions, the name is usually omitted. A function with no name is called an anonymous function.

IMMEDIATELY INVOKED FUNCTION EXPRESSIONS

This way of writing a function is used in several different situations. Often functions are used to ensure that the variable names do not conflict with each other (especially if the page uses more than one script).

VARIABLE SCOPE

The location where you declare a variable will affect where it can be used within your code. If you declare it within a function, it can only be used within that function. This is known as the variable’s scope.