Javascript Reference Card (Page 5 of 6) in pdf

FUNCTIONS

PUTTING IT TOGETHER:

JAVASCRIPT AND HTML

Definition: A pre-written block of code that performs a

ON THE WEB

specific task. Some functions return values; others perform

a task like sorting, but return no value. Function names

Cookies: Text-file messages stored by the browser on the

follow the same rules as variables names. There may or

user’ s computer

may not be an argument or parameter in the parenthesis,

Purpose: To identify the user, store preferences, and present

but the parenthesis has to be there.

customized information each time the user visits the page

User-defined Functions:

Types:

Example:

Temporary (transient, session) — stored in temporary

ParseInt() or ParseFloat() convert a string to a

memory and available only during active browser session

number.

Persistent (permanent, stored) — remain on user’ s comput-

To create a function:

er until deleted or expired

Format:

Browser Detection: A script written to determine which

function name_of_function (arguments) {

browser is running; determine if the browser has the capabili-

statements to execute when

ties to load the webpage and support the javascript code; and,

function is called;

if needed, load alternate javascript code to match the browser

}

and platform.

Example:

Sniffing: A script written to determine whether a specific

function kilosToPounds (){

browser feature is present; i.e., detecting the presence of

pounds=kilos*2.2046;

Flash before loading a webpage.

}

Event Handling: Use HTML event attributes (mouseover,

This new function takes the value of the variable kilos,

mouse click, etc.) and connect event to a JavaScript function

multiplies it by 2.2046, and assigns the result to the vari-

called an event handler

able pounds.

To call a function: Give the name of the function followed

by its arguments, if any

ParseInt(X); converts the data stored in the variable

X into a numeric value.

kilosToPounds(17); converts 17 kilos to the same

mass in pounds, returning the value 37.4782.

METHODS

Definition: A special kind of function used to describe or

instruct the way the object behaves. Each object type in

JavaScript has associated methods available.

Examples:

array.sort();

document.write();

string.length();

Calling: To call or use a method, state the method name

followed by its parameters in parentheses.

Example:

document.write(“Hello, world!”);

Javascript Reference Card Page 5

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