Directions for Starting a Car.
Walk to the driver's side of the car.
Get the key into our hand.
Locate the keyhole on the driver-side door.
Placing the end that is not ridged between your thumb and index finger, insert the ridged part into the key hole on the driver-side door.
Turn the key clock-wise until you hear clicking/unlocking sound.
Remove the key.
Lift the door handle and open the driver-side door.
Swing the door all the open so that you can enter the car with your body.
Sit in the seat, to do this you place your butt into the seat.
What we learn from this exercise:
Before we start writing code we should start with psuedo-code and write in plain English the steps we plan to take.
Create a new "site" in Dreamweaver (specify the folder where all the files will be).
Into the head:
F12 (runs the page)
alert - is just giving you one of those alert boxes
It makes a difference where you put the code. Generally we put the code into the head of the page.
Script in the head =
If you add some text to the body and then view the page, the alert will pop up before you are able to see whatever you typed into the body.
Script in the body =
So if you put the alert into the body after the paragraph text in the body, you will see the body text before the alert.
/* multi-line comment */
In the body
document.write("hello world, but this time it's better.");
Grammar (aka syntax) of JS
Statements = usually represents a single step in a program
statements end with a semicolon;
"Commands" (commands is not an official title, just something we made up for this class) = functions or methods, they use parenthesis ( blah do something blah )
Variable = container for data, a placeholder
for example if we have the variable called name : we all have a name but since that name is different that variable called name has a different value.
= this is not an equal sign, it is the assignment operator meaning: set to the value of
equals is a completely different thing
2 Steps to create a variable:
- declare the variable var name;
- assign it a value name = "J-cubed";
-or- var name = "J3";
<h1>I am thirsty.</h1>
var message; //declared a variable
message = "hello world, but this time it's better." //assign it a value
document.write(message); //write the message out to the page
In JS it can only begin with a letter, $, or and _
var name, var $name, var _name
They can contain letters, numbers, $, _, camelCase BUT NO SPACES
The variables are case sensitive
Variable Data Types
every variable you make has a specific data type, it tells you what kinda stuff is in that container
Also it informs you what you can do with it.
For example if you have a number you know you can do math on it, as opposed to a string.
We will be dealing 3 common data types:
Number- 5, 5.3, -5.3
String - any series of alphanumeric characters that are enclosed in quotes (you can use single or double quotes)
Boolean - true or false
var myVar ="5" this is a string
var myVar=5 this is a number
But you can't put a carriage return in the middle of a string