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JavaScript Popup Boxes

Alert Box

An alert box is often used if youwant to make sure information comes

through to the user.

Syntax: alert("sometext");

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Continues.

Confirm Box

A confirm box is often used if you want theuser to verify or accept something. Returns

true or false.

Syntax:

confirm("sometext");

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Continues

Prompt Box

A prompt box is often used if you wantthe user to input a value before entering

a page. Returns the input value or null.

Syntax:prompt("sometext","defaultvalue");

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JavaScript Events

Events are actions that can be detected by

JavaScript.

Examples of events:A mouse click

A web page or an image loading

Mouse over a hot spot on the web page

Selecting an input field in an HTML form

Submitting an HTML form

A keystroke

Note: Events are normally used in combination with functions, and the

function will not be executed before the event occurs!

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Event ObjectThe Event object represents the state of an event, such as

the element in which the event occurred, the state of the

keyboard keys, the location of the mouse, and the state of themouse buttons.

Event Handlers (Attributes)

onabort, onblur, onchange, onclick, ondblclick, onerror,

onfocus, onkeydown, onkeypress, onkeyup, onload,onmousedown, onmousemove, onmouseout, onmouseover,

onmouseup, onreset, onresize, onselect, onsubmit, onunload

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JavaScript Exception Handling The try...catch Statement:

The try...catch statement allows you to test a block of

code for errors. The try block contains the code to be run,and the catch block contains the code to be executed ifan error occurs.

try

{

//Run some code here

}

catch(err)

{

//Handle errors here}

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JavaScript Throw Statement

The throw statement allows you to create an

exception. If you use this statement togetherwith the try...catch statement, you can control

program flow and generate accurate error

messages.

Syntax:throw(exception)

ht l

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var x=prompt("Enter a number between 0 and 10:","");

try {

if(x>10) {

throw "Err1";

}else if(x

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JavaScript Special Characters The backslash (\) is used to insert apostrophes, new

lines, quotes, and other special characters into a text

string. Code Outputs

\' single quote

\" double quote

\& ampersand

\\ backslash

\n new line

\r carriage return

\t tab

\b backspace\f form feed