Javascript Faq [Archive] - HTML Forums - Free Webmaster Forums and Help Forums

Jon Hanlon

01-14-2002, 04:33 PM

To format a number to a fixed number of decimal places, use:

function formatNumber(expr, decimals) {
var str = "" + Math.round( eval(expr) * Math.pow(10,decimals))
while (str.length <= decimals) { str = "0" + str }
var decpoint = str.length - decimals;
var result = str.substring(0,decpoint);
if (decimals) result += "." + str.substring(decpoint,str.length);
return result;
}
var someNumber = 786/7
var sixPlaces = (someNumber,6)
var noDecimals = formatNumber(someNumber)
var pi4 = formatNumber(355/113,4)

Dr. Web

01-16-2002, 01:37 PM

HTML/ Javascript Faq

Q. How do I set the focus to elements on the page?

A. By using an event handler coupled with JavaScript.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>Untitled</title>
</head>
<body>
<form>
<input type=button value="Focus On Link" onClick="document.links[0].focus()">
<input type=button value="Focus On Text Field" onClick="document.forms[0].text1.focus()">
<input type=button value="Focus On Select Box" onClick="document.forms[0].select1.focus()">
<input type=button value="Focus On Radio Button" onClick="document.forms[0].radio1.focus()">
<input type=button value="Focus On a Button" onClick="document.forms[0].button1.focus()">
<br><br><br>
            <a href="blah">here</a>
                  <input type=text name=text1>
              <select name=select1>
<option selected>Choose One...</option>
<option>Option1</option>
<option>Option2</option>
</select>
                               <input type=radio name=radio1>
                               <input type=button value="Sample Button" name=button1>
</form>
</body>
</html>

Dr. Web

01-16-2002, 01:38 PM

JavaScript Faq

Q. How do I verify that a email address is entered correctly?

A. Use JavaScript to inspect the entry. The following code only returns a alert if the email address is not valid.

<html>
<head>
<script language="JavaScript">

</script>
</head>
<body>
<form name=form1>
<br>
<input type=text name=email size=15>
   
<input type=button onClick="IsEmailValid()" value="verify email address">
</form>
</body>
</html>

Dr. Web

01-17-2002, 06:30 PM

JavaScript Faq

Q. How do I automatically round nunmbers that the user enters?

A. With a handy bit of JavaScript.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled</title>
<script language=javascript>
function roundAmount(amount, where)
{
var s = "";
var decimal;
amount = parseFloat(amount);
if (!(isNaN(amount))) {
// round to nearest cent
amount = Math.round(amount * 100);
amount = amount / 100;

// format the output
s = new String(amount);
decimal = s.indexOf(".");
if (decimal == -1) {
// whole number
s+= ".00";
} else {
if (decimal == (s.length - 2)) {
// needs a trailing zero
s+= "0";
}
}
} else {
// not a number so return zero
s = "0.00";
}
where.value=s;
return s;
}
</script>
</head>

<body>
<form>
<input type=text name=numbers onBlur="roundAmount(this.value, this)">
<input type=button value="Click Me!">
</form>
</body>
</html>

Dr. Web

01-18-2002, 01:23 PM

JavaScript Faq

Q. How do I limit the characters in a textarea?

A. Use a little JavaScript, and all will be well!

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled</title>
<SCRIPT LANGUAGE="JavaScript">










</script>
</head>
<body>
<form name=form1>
<textarea name=content cols=70 rows=18 onKeyDown="textCounter(this.form.content,this.form.remLen,4000);"
onKeyUp="textCounter(this.form.content,this.form.remLen,4000);"
onFocus="textCounter(this.form.content,this.form.remLen,4000);">
</textarea>
<br><br>
<input readonly type=text name=remLen size=2 maxlength=3 value="4000" style="border: 1px;"> characters left</font>
</form>
</body>
</html>

Jon Hanlon

01-22-2002, 07:26 PM

When scripting Javascript, do not use a keyword as an identifier.
Current and reserved future keywords are:

abstract else instanceof switch
boolean enum int synchronized
break export interface this
byte extends long throw
case false native throws
catch final new transient
char finally null true
class float package try
const for private typeof
continue function protected var
debugger goto public void
default if return volatile
delete implements short while
do import static with
double in super

When naming identifiers it is also important to avoid any words that are
already the names of intrinsic Javascript objects, properties, methods
or functions, such as Date, PI, test or escape.

Jon Hanlon

01-28-2002, 04:31 PM

You cannot change the Chrome of the current window. You can open a new window and specify the Chrome (status bar, location field, menubar, toolbar etc.), but you cannot change the current window's settings.
The reasoning behind this is to stop rogue sites from hiding the back button, location field etc. thus making it difficult for users to leave the site.

Jon Hanlon

02-03-2002, 05:48 PM

For IE5+, you can set the homepage by doing:
<a href="javascript:void(0)"
onclick="this.style.behavior='url(#default#homepage)';this.setHomePage('http://www.yourSite.com');">
Make us your Homepage
</a>
Note that the user must confirm that this is OK.

Mark

03-22-2002, 06:57 PM

Javascript FAQ

Q: How do I block javascript errors?
A: Insert the following code between your <head> tags:

<head>
<script type="text/javascript" language="javascript">
window.onerror = function(){return true;}
</script>
</head>

Jon Hanlon

07-08-2002, 08:36 PM

HTML is a stateless (http://www.webopedia.com/TERM/s/stateless.html)
protocol, which means that it has the memory of a goldfish. Every page is
unaware of what happened previously, and it is difficult to pass variables
from one page to the next. There are three non-server related methods
for maintaining state:

Cookies
Frames
URL Search property

Cookies
Can be set and then read by the next page. There are heaps of Cookie How To's
around. Most functions are based on Bill Dortch's public domain functions.
eg. See http://www.webdeveloper.com/javascript/javascript_html_tnt_cookies.html
The disadvantage of cookies is that they can be turned off by the user.

Frames
The topmost window or a static banner frame can be used to store variables
whilst other frames change. Useful is the special keyword top which
refers to the page containing the first frameset.
eg. top.favoriteFood = "Ice Cream" , parent.frames.banner.myName="Lee"
The disadvantage is that frames may be impractical.

URL Search property
The location object includes protocol, host, pathname, hash and search, so
we can load up the search property to suit our needs.
The disadvantage is that the user can see (and possibly alter) the data, so
if you're passing anything important it's best to encrypt it with several
check digits.

An example illustrates:

Page 1

<form>
<input type="button" onclick="nextPage('Disney')" value="Disney Ducks">
<input type="button" onclick="nextPage('Warner')" value="Warner Ducks">
</form>

<script language="Javascript">
function nextPage(strStudio) {
var strSearch = "?studio=" + strStudio;
if (strStudio == "Warner") strSearch += "&ducks=Daffy";
if (strStudio == "Disney") strSearch += "&ducks=Huey+%2C+Duey+%26+Looey";
var newLocation = "http://www.someSite.com/Page2.html" + strSearch

location.assign(newLocation)
}
</script>

This page simply navigates to the next page using either
http://www.someSite.com/Page2.html?studio=Disney&ducks=Huey+%2C+Duey+%26+Looey
or
http://www.someSite.com/Page2.html?studio=Warner&ducks=Daffy

Note that we replace spaces by plus(+) signs, and punctuation by the ascii code
(comma = %2C Ampersand = %26).

The next page needs to examine the search property of the URL:
Page 2

<script language="Javascript">
function plusUnescape(str) { // the unescape function won't convert plus signs
str = '' + str; // to spaces; like you see in search strings
while (true) {
var j = str.indexOf('+');
if (j == -1) break;
str = str.substring(0,j) + ' ' + str.substring(j+1,str.length);
}
return unescape(str);
}

function getArgument (theKey) {
var args = new Array ();
var argstring = window.location.search;
if (argstring.charAt(0) != '?') return false;
argstring = argstring.substring(1, argstring.length);
var argarray = argstring.split('&');
for (var j=0; j < argarray.length; j++) {
var singlearg = argarray[j].split('=');
if (singlearg.length != 2) continue; // not a valid argument
var argsKey = plusUnescape(singlearg[0]);
var argsValue = plusUnescape(singlearg[1]);
args [argsKey] = argsValue;
}
return args[('' + theKey)]
}

function whichDucks() {
var strStudio = getArgument("studio")
if (!strStudio) return false; // nothing passed
var strDucks = getArgument("ducks")
alert("The " + strStudio + " studio created the duck(s) " + strDucks)
}
</script>

<form>
<input type="button" onclick="whichDucks()" value="Which Ducks">
</form>

Jason

03-21-2003, 12:55 AM

Originally posted by Dr. Web
JavaScript Faq

Q. How do I limit the characters in a textarea?

A. Use a little JavaScript, and all will be well!

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled</title>
<SCRIPT LANGUAGE="JavaScript">










</script>
</head>
<body>
<form name=form1>
<textarea name=content cols=70 rows=18 onKeyDown="textCounter(this.form.content,this.form.remLen,4000);"
onKeyUp="textCounter(this.form.content,this.form.remLen,4000);"
onFocus="textCounter(this.form.content,this.form.remLen,4000);">
</textarea>
<br><br>
<input readonly type=text name=remLen size=2 maxlength=3 value="4000" style="border: 1px;"> characters left</font>
</form>
</body>
</html>

Found a NS 7.02 bug on this one. It shows 400 chars left instead of 4000, and deducts 1 char every 10 chars (so maybe it is a display problem since it will still stop you at 4000 chars even with the bug)?

scoutt

03-21-2003, 01:03 AM

here Jason, just replace this with what you got.

<SCRIPT LANGUAGE="JavaScript">










</script>

code in html
Maximum Number of characters for this text box is 250.<br>
<TEXTAREA onKeyDown="textCounter(this.form.CustomVerseText,this.form.remLen,250);"
onKeyUp="textCounter(this.form.CustomVerseText,this.form.remLen,250);"
onFocus="textCounter(this.form.CustomVerseText,this.form.remLen,250);"
name=CustomVerseText rows=7 wrap=physical cols=60 maxLength="250"></TEXTAREA>
<br><br>

You have <B><input type="text" readonly name=remLen size=2 maxlength=3 value="250" style="border: 1px;"></B>characters remaining
for your description...</font>

I have it set to 250 and it worked in Mozilla so it should work in all of them.