Counter Script - Javascript

Papajo

This simple script counts up or down with a button click, now can it be
modified so the count won't go below zero?
********** Thanks, Joe

<form>
<input type=text name=amount size=4 value=>
<input type=button value="up"
onClick="javasc ript:this.form. amount.value++; ">
<input type=button value="down"
onClick="javasc ript:this.form. amount.value--;">
</form>

Sep 30 '05 #1

Subscribe Reply

2590

web.dev

Papajo wrote:

This simple script counts up or down with a button click, now can it be
modified so the count won't go below zero?
Thanks, Joe

<form>
<input type=text name=amount size=4 value=>
<input type=button value="up"
onClick="javasc ript:this.form. amount.value++; ">
<input type=button value="down"
onClick="javasc ript:this.form. amount.value--;">
</form>

There is no need for the javascript protocol. I prefer not to do
inline javascript unless I can't help it.

Place script in between the <head> tags and you can something like the
following:

<script type = "text/javascript">
function countUp(obj)
{
obj.form.amount .value++;
}

function countDown(obj)
{
amtObj = obj.form.amount ;

if(amtObj.value > 1)
{
obj.form.amount .value--;
}
}
</script>

As for your form:

<form>
<input type = "text" name = "amount">
<input type = "button" value = "up" onClick = "countUp(this); ">
<input type = "button" value = "down" onClick = "countDown(this );">
</form>

Sep 30 '05 #2

Lee

Papajo said:

This simple script counts up or down with a button click, now can it be
modified so the count won't go below zero?
=A0=A0=A0=A0=A 0=A0=A0=A0=A0=A 0 Thanks, Joe

<form>
<input type=3Dtext name=3Damount size=3D4 value=3D>
<input type=3Dbutton value=3D"up"
onClick=3D"jav ascript:this.fo rm.amount.value ++;">
<input type=3Dbutton value=3D"down"
onClick=3D"jav ascript:this.fo rm.amount.value--;">
</form>

<form>
<input type="text" name="amount" size="4" value="0">
<input type="button" value="up"
onClick="this.f orm.amount.valu e++;">
<input type="button" value="down"
onClick="if(thi s.form.amount.v alue>'0')this.f orm.amount.valu e--;">
</form>

Sep 30 '05 #3

Evertjan.

Lee wrote on 30 sep 2005 in comp.lang.javas cript:

Papajo said:

<form>
<input type="text" name="amount" size="4" value="0">
<input type="button" value="up"
onClick="this.f orm.amount.valu e++;">
<input type="button" value="down"
onClick="if(thi s.form.amount.v alue>'0')this.f orm.amount.valu e--;">
</form>

this.form.amoun t.value>'0'
the parentheses are unnecessary.
Much better to disable the down button when 0 is reached:

=============== =========
<form>

<input type="text" name="amount" size="4" value="2">

<input type="button" value="up"
onClick="this.f orm.amount.valu e++;
document.getEle mentById('down' ).disabled=fals e">

<input type="button" value="down" id='down'
onClick="this.d isabled=(--this.form.amoun t.value==0);">

</form>
=============== ==========

ie6 tested

--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)

Sep 30 '05 #4

Lee

Evertjan. said:

Lee wrote on 30 sep 2005 in comp.lang.javas cript:
Papajo said:

<form>
<input type="text" name="amount" size="4" value="0">
<input type="button" value="up"
onClick="this.f orm.amount.valu e++;">
<input type="button" value="down"
onClick="if(thi s.form.amount.v alue>'0')this.f orm.amount.valu e--;">
</form>

this.form.amou nt.value>'0'
the parentheses are unnecessary.
Much better to disable the down button when 0 is reached:

============== ==========
<form>

<input type="text" name="amount" size="4" value="2">

<input type="button" value="up"
onClick="this.f orm.amount.valu e++;
document.getEle mentById('down' ).disabled=fals e">

<input type="button" value="down" id='down'
onClick="this.d isabled=(--this.form.amoun t.value==0);">

</form>

How is that much better? It's insignificantly more efficient
in execution, and much more complicated to implement (and for
a new user to understand).

Sep 30 '05 #5

Dr John Stockton

JRS: In article <28************ ****@storefull-3337.bay.webtv. net>,
dated Fri, 30 Sep 2005 14:04:09, seen in news:comp.lang. javascript,
Papajo <do*****@webtv. net> posted :

This simple script counts up or down with a button click, now can it be
modified so the count won't go below zero?
********** Thanks, Joe

<form>
<input type=text name=amount size=4 value=>
<input type=button value="up"
onClick="javas cript:this.form .amount.value++ ;">
<input type=button value="down"
onClick="javas cript:this.form .amount.value--;">
</form>

Consider and adapt

<input type=button value="5"
onClick="javasc ript:this.value -= this.value>0">

Read the newsgroup FAQ for other matters.

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
<URL:http://www.jibbering.c om/faq/> JL/RC: FAQ of news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htm> jscr maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links.

Sep 30 '05 #6

Papajo

Thank you for the responses, I went with Lee's script, it was the
easiest and best for my application. Joe

<form>
<input type="text" name="amount" size="4" value="">

<input type="button" value="up"
onClick="javasc ript:this.form. amount.value++; ">
<input type="button" value="down"
onClick="if(jav ascript:this.fo rm.amount.value >'0')this.form. amount.value--;">
</form>

Oct 1 '05 #7

Robi

Dr John Stockton wrote in message news:uF******** ******@merlyn.d emon.co.uk...

Papajo posted:
This simple script counts up or down with a button click, now can it be
modified so the count won't go below zero?
Thanks, Joe

<form>
<input type=text name=amount size=4 value=>
<input type=button value="up"
onClick="javasc ript:this.form. amount.value++; ">
<input type=button value="down"
onClick="javasc ript:this.form. amount.value--;">
</form>

Consider and adapt

<input type=button value="5"
onClick="javasc ript:this.value -= this.value>0">

Read the newsgroup FAQ for other matters.

hmmm...
three questions:
1. why the "javascript :" in onClick="javasc ript:this.value -= this.value>0">
2. if I want to go up, I run into "string" problems:

<input type=text name=amount size=4 value=5>
<input type=button value="down"
onClick="this.f orm.amount.valu e -= this.form.amoun t.value>0">

works wonderfully, but

<input type=button value="up"
onClick="this.f orm.amount.valu e += +this.form.amou nt.value<10">
returns 5true (5truefalse on the next...)
<input type=button value="up"
onClick="this.f orm.amount.valu e += +(this.form.amo unt.value<10)">
returns 51 (and 510 on the second click)

I thought unary+ would type-convert to number, but I notice:
stringVar += +stingVar --> stringVar += numVar

so I end up with
<input type=button value="up"
onClick="this.f orm.amount.valu e = +this.form.amou nt.value + +(this.form.amo unt.value<10)">

isn't there a shortcut or is type-conversion only really good for - * and /?

ok, came up with the unpretty:
<input type=button value="up"
onClick="this.f orm.amount.valu e -= +(this.form.amo unt.value<10) * -1">

this way, the -= type-converts both sides additionally I need to invert the number (- * - = +)

Oct 1 '05 #8

Evertjan.

Lee wrote on 01 okt 2005 in comp.lang.javas cript:

Evertjan. said:

Lee wrote on 30 sep 2005 in comp.lang.javas cript:
Papajo said:

<form>
<input type="text" name="amount" size="4" value="0">
<input type="button" value="up"
onClick="this.f orm.amount.valu e++;">
<input type="button" value="down"
onClick="if(thi s.form.amount.v alue>'0')this.f orm.amount.valu e-
-;">
</form>

this.form.amo unt.value>'0'
the parentheses are unnecessary.
Much better to disable the down button when 0 is reached:

============= ===========
<form>

<input type="text" name="amount" size="4" value="2">

<input type="button" value="up"
onClick="this.f orm.amount.valu e++;
document.getEle mentById('down' ).disabled=fals e">

<input type="button" value="down" id='down'
onClick="this.d isabled=(--this.form.amoun t.value==0);">

</form>

How is that much better? It's insignificantly more efficient
in execution, and much more complicated to implement (and for
a new user to understand).

The much better is the computer/human interface showing that the down-
button does not function when the value is zero.

A down button that looks and feels functinal but does not count down is a
bad concept, when disabling is possible.

Proramming is not only about functioning but also about functionality.

--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)

Oct 1 '05 #9

Papajo

To answer your question about the "javascript :" in the onClick is that
this script is being used on a simple webtv browser, it wouldn't work
without it. Thanks again Joe
PS: sorry I didn't mention it in my original post

Oct 1 '05 #10

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