I'm new to JavaScript and I wrote this code to play with. Oddly, if I
enter text in a box and then press the button, I only get the onChange
event for the text box and not the button's onclick event. But if I
press the button without entering text first, the button click event
does work. What's up?
<html>
<body>
<h3>Events on Buttons and Text Boxes</h3>
<input id="myTextBox1 " type="text" onChange="doCha nge1()" /<br />
<input id="myTextBox2 " type="text" onChange="doCha nge2()" /<br />
<input id="myButton" type="button" onclick="doClic k()" value="Click me"
/>
<script type="text/javascript">
function doChange1(e)
{
var val = document.getEle mentById("myTex tBox1").value;
alert("You typed: " + val);
}
function doChange2(e)
{
var val = document.getEle mentById("myTex tBox2").value;
alert("You typed: " + val);
}
function doClick(e)
{
var _num = prompt("Enter a number", "100");
alert("You typed: " + _num); // number converted to string
automatically
}
</script>
</body>
</html>
Nov 16 '06
17  9680 
ASM said the following on 11/16/2006 9:11 PM:
Eric a écrit :
>David Golightly wrote:
>>Eric wrote:
4. In your onClick handler, you should understand that _num is always a
string (whether it contains digits or not), it's never a number. If
you wanted an actual number you could do math with, you need to call
parseInt(_num ).
Thanks for this clarification, also. I'm not used to a typeless
language that really does have types, and I assumed the conversion
would always be automatic. But in my code I wasn't trying to do math on
it, anyway. I guess if I tried to add 1 it would have blown up unless I
had the parseInt.
Say a number in a text field :
var n = document.myForm .myTextField.va lue; // n is text
n = n*1; // number
n = +n; // number
n = Number(n); // number
n = parseInt(n); // number
var n = "09";
k = parseInt(n);
alert(k); //0
Don't use parseInt without the Radix unless you know for absolute
certainty that it doesn't contain a leading 0 or 0x
<URL: http://jibbering.com/faq/#FAQ4_12>
--
Randy
Chance Favors The Prepared Mind
comp.lang.javas cript FAQ - http://jibbering.com/faq
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/
In message <11************ **********@h48g 2000cwc.googleg roups.com>, Thu,
16 Nov 2006 18:26:26, David Golightly <da******@gmail .comwrites
>
Not exactly. In JS the following is true:
'1' + '1' == '1' + 1 == '11'
Actually, executed as JS, that gives false .
>The + operator is used to concatenate strings, and anything that's not
a string, when added to a string, is automatically converted rather
than throwing an error.
It does, however, convert a Boolean to a Number, and a Function to NaN.
It's a good idea to read the newsgroup and its FAQ. See below.
--
(c) John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v6.05 IE 6
<URL:http://www.jibbering.c om/faq/ Old RC FAQ of news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htmjscr maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/TP/BP/Delphi/jscr/&c, FAQ items, links.
Dr J R Stockton wrote on 18 nov 2006 in comp.lang.javas cript:
>>'1' + '1' == '1' + 1 == '11'
Actually, executed as JS, that gives false .
True, it does.
Try:
alert( '1' + '1' == '1' + 1 == '11' ) // false, because:
alert( ('1' + '1') == ('1' + 1) == '11' ) // false
alert( '1' + ('1' == '1') + (1 == '11') ) // 1truefalse
// btw:
alert( '1' + 1 === '11' ) // true
--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)
In message <Xn************ *******@194.109 .133.242>, Sat, 18 Nov 2006
10:40:53, Evertjan. <ex************ **@interxnl.net writes
>Try:
alert( '1' + '1' == '1' + 1 == '11' ) // false, because:
I can try it without the alert( or the ) . I just copy from one
window, paste into another, and press "Eval".
--
(c) John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v6.05 IE 6
<URL:http://www.jibbering.c om/faq/ Old RC FAQ of news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htmjscr maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/TP/BP/Delphi/jscr/&c, FAQ items, links.
Dr J R Stockton wrote on 18 nov 2006 in comp.lang.javas cript:
I can try it without the alert( or the ) . I just copy from one
window, paste into another, and press "Eval".
I have heard one could press charges, but
how the (d)evil does one press eval?
--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)
<html>
<body>
<textarea id="jscode">
</textarea>
<input type="button"
onclick="alert( eval(document.g etElementById(' jscode').value) )"
value="Eval" />
</body>
</html>
that's how.
David Golightly wrote on 19 nov 2006 in comp.lang.javas cript:
that's how.
That's how what, David?
Please quote on usenet, this is not email.
--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)
In message <Xn************ *******@194.109 .133.242>, Sat, 18 Nov 2006
23:39:31, Evertjan. <ex************ **@interxnl.net writes
>Dr J R Stockton wrote on 18 nov 2006 in comp.lang.javas cript:
>I can try it without the alert( or the ) . I just copy from one
window, paste into another, and press "Eval".
I have heard one could press charges, but
how the (d)evil does one press eval?
"Eval", not "eval".
The window to be copied into can be left open, and at least partly
visible on the screen, and "Eval" is written on the first button. One
moves the mouse so that ... .
The window in question is one showing a local copy of my Web page
<URL:http://www.merlyn.demo n.co.uk/js-quick.htm>.
To see how it works, get that page, press "Demo" 6N+5 times then press
Eval (NewW only works with some Demo numbers). Demos 2, 3, & 6 are
better examples of normal use.
But read the rest of the page too.
--
(c) John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v6.05 IE 6
<URL:http://www.jibbering.c om/faq/ Old RC FAQ of news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htmjscr maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/TP/BP/Delphi/jscr/&c, FAQ items, links. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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