JavaScript Basics 1

Variables

- The keyword var is used to define a variable.
- Variable names can contain numbers, the dollar symbol ($) and underscores (_)
- Variable names can begin with $ or _ but not numbers
- In JavaScript strings can be enclosed in single quotes or double quotes. I guess you could use single quotes quotes whenever you need double quotes inside a string.


Examples
A String          - var question1 = "What is Kenny's address?"
An Integer      - var int = 728
A Float           - var $pr = 7.28


Concatenation
Basically this is combining strings with a plus symbol.

Examples

var firstName = "Victor";
var lastName   = "Wooding";
var fullName = firstName + lastName;


Updating a Variable
This is a very important method that you will use frequently in JavaScript

Example

var message = "John Brown wears a bowtie.";
message += " He also likes to wear suspenders."
message += " John Brown is a good man.";

alert(message);

What will the alert message print?

Getting User Input
It is possible to get the user to enter information using the prompt() function.

You could use it to ask a question and store the response in a variable

Example

var feeling = prompt('Use one word to describe how you feel.');
alert("Victor feels " + feeling + " today!");

What do the above lines of code print?

The prompt method always requires a string.

Writing to the Webpage
It is possible to write to the webpage using the document.write() function.

Example
Continuing from above you could write.

var feeling = prompt('Use one word to describe how you feel.');
document.write("Victor feels " + feeling + " today!");


you could adjust the size of the text by enclosing it in a header. Pay close attention to the syntax.

document.write("<h3>Victor feels " + feeling + " today!</h3>");