Wednesday, April 27, 2011

Chapter 4 - Notes

Words, Numbers, and Dates

JavaScript made up of Objects.
Properties - parts of the object.
Methods - actions and object perform.

Object - array
Properties - length
Method - push()

Object - document
Method - write

Whenever you create a new variable and store a value into it, you are creating an instance.


to determine the length of a string:

var password = 'sesame';   
if (password.length <= 6) {  
   alert('That password is too short.');  
} else if (password.length > 15) { 
    alert('That password is too long.'); 

Chang the Case of a String

The correct answer to a quiz is LeCuyer, but the person types Lecuyer so they get it wrong.
To correct you can covert both the response and the correct answer to uppercase
if (response.toUpperCase() == correctAnswer.toUpperCase()) {
} else {

Covert to lowercase:
var answer= 'LeCuyer'; 

returns :   lecuyer

In both cases the original string is not altered, it is still LeCuyer.

Searching a String: indexOf()
To find out which browser the viewer is using:
Navigator is an object of the web browser, userAgent is the property

 <script type="text/javascript">

if the search string isn't found the method returns: -1
var browser = navigator.userAgent; // this is a string
if (browser.indexOf('MSIE') != -1) {
// this is Internet Explorer

if the searched string is found it returns the position number.
(spaces count as a position:  poop face  has 0-8

var myString = "Poop Face";
var firstPosition = myString.indexOf('Poo'); // returns 0
var lastPosition = myString.lastIndexOf('Face'); // returns 5

This picks the 6th position of the string.

The end is actually the last position +1.
so (0,5) selects the first five letters/positions 0-6

you can also use negative numbers

Regular Expressions
var myMatch = /hello/; 
this matches the word hello

How to search using the search() Method
var myRegEx = /To be/; 
var quote = 'To be or not to be.';
var foundPosition =;   //returns 0, it returns the first position in the match

No comments:

Post a Comment