Board index » javascript » what does this.value.replace().replace() do?

2008-02-06 04:32:07 AM
Hello,
Amrit has posted the code below for keeping the focus on a text box
until some text is entered.
Can someone please explain how
{if(this.value.replace(/^\s+/,"").replace(/\s+$/,"") == "") focus();}
works - I don't understand the
this.value.replace().replace() part....
Thanks
Geoff
function focus() {
if(typeof document.MyForm.username.onblur != "function")
document.MyForm.username.onblur = function()
{if(this.value.replace(/^\s+/,"").replace(/\s+$/,"") == "") focus();}
alert("please add your first and last names before continuing");
document.MyForm.username.focus();
}
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On Feb 6, 6:32 am, Geoff Cox <<>>wrote:
support it:
this.focus();
or more cautiously:
this.focus && this.focus();
.replace is a reference to the replace method of the string, it
returns a string.
(/^\s+/,"") calls the replace method with the enclosed arguments,
the first is a regular expression that matches one or more whitespace
characters at the start of the string. The second is the replacement
text, an empty string. The returned string will have all leading
whitespace removed.
.replace(/\s+$/,"") similar to the above, but removes all trailing
whitespace.
The test essentially determines if the value of the element consists
only of zero or more whitespace characters.
A shorter equivalent is:
if (/^\s*$/.test(this.value)) {
...
}
Rob
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Geoff Cox < wrote on 05 feb 2008 in comp.lang.javascript:
(this.value.replace(/^\s+/,"").replace(/\s+$/,"") == "")
is a silly long way of writing:
( !/\S/.test(this.value) )
============================
2 focus() must be appended to an object that supports it:
like
document.getElementById('theId').focus();
or
this.focus();
--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)
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Geoff Cox < wrote:
string. The second replace call is just operating on that string.
It's equivalent to this:
var x=this.value.replace();
var y=x.replace();
You could do something crazy like this:
var s="hello world";
alert(s.replace("hello","goodbye").replace("goodbye","hello"));
The first call would return a string of "goodbye world", and the second
call would return a string of "hello world" which would get alerted.
none of the calls would modify s though.
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On Tue, 05 Feb 2008 22:22:53 +0100, Stevo <please@spam-me.com>wrote:
Cheers
Geoff
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On 05 Feb 2008 21:22:21 GMT, "Evertjan."
<exjxw.hannivoort@interxnl.net>wrote:
function focus() {
if(typeof document.sliderForm.username.onblur != "function")
document.sliderForm.username.onblur = function()
{if( !/\S/.test(this.value) ) focus();}
alert("please add your first and last names before continuing");
document.sliderForm.username.focus();
}
with IE 7 it repeatedly brings up the alert when I click out of the
text box but with Firefox 2 this happens a couple of times and then I
can click outside the box but get no alert...can this be changed for
Firefox?
Cheers
Geoff
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In comp.lang.javascript message <pohhq3t5cpaprgn2lei9lulfh0al8r185u@4ax.
com>, Tue, 5 Feb 2008 20:32:07, Geoff Cox <?@?.?.invalid>posted:
valid.htm>; and what the latter links to.
It's a good idea to read the newsgroup c.l.j and its FAQ. See below.
--
(c) John Stockton, nr London UK. ?@merlyn.demon.co.uk IE6 IE7 FF2 Op9 Sf3
<URL:www.merlyn.demon.co.uk/js-index.htm>jscr maths, dates, sources.
<URL:www.merlyn.demon.co.uk/>TP/BP/Delphi/jscr/&c, FAQ items, links.
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