FAQ Topic - How do I access a property of an object using a string?

[FAQ server]

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FAQ Topic - How do I access a property of an object using a string?
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There are two equivalent ways to access properties: the dot
notation and the square bracket notation. What you are looking
for is the square bracket notation in which the dot, and the
identifier to its right, are replaced with a set of square
brackets containing a string. The value of the string matches
the identifier. For example:-

//dot notation
var bodyElement = document.body;

//square bracket notation, using an expression
var bodyElement = document["bo"+"dy"];

http://www.jibbering.com/faq/faq_not..._brackets.html
===
Postings such as this are automatically sent once a day. Their
goal is to answer repeated questions, and to offer the content to
the community for continuous evaluation/improvement. The complete
comp.lang.javas cript FAQ is at http://www.jibbering.com/faq/.
The FAQ workers are a group of volunteers.

[John G Harris]

In article <Y9************ **@invalid.uk.c o.demon.merlyn. invalid>, Dr J R
Stockton <jr*@merlyn.dem on.co.ukwrites

>In message <45************ ***********@new s.sunsite.dk>, Sat, 18 Nov 2006
00:00:01, FAQ server <ja********@dot internet.bewrit es

>>
There are two equivalent ways to access properties: the dot notation
and the square bracket notation. What you are looking for is the square
bracket notation in which the dot, and the identifier to its right, are
replaced with a set of square brackets containing a string. The value
of the string matches the identifier. For example:-

//dot notation
var bodyElement = document.body;

//square bracket notation, using an expression
var bodyElement = document["bo"+"dy"];

http://www.jibbering.com/faq/faq_not..._brackets.html

Properties can be addressed by dot notation and by square bracket
notation.

Dot notation is appropriate where the "term" is known at programming
time.

Dot notation is not appropriate when the property name does not obey the
rules for identifiers.

>Square bracket notation is necessary if the "term" must be supplied at
run time.

"term" is pretty woolly. What's wrong with property name? It's explicit
and accurate.

John
--
John Harris

[John G Harris]

In article <GO************ ********@telcov e.net>, Randy Webb
<Hi************ @aol.comwrites

<snip>

>PHP's array-ness of inputs comes to mind first. If the name of the
inputs is "myInput[]" then you have to use bracket notation to access
it using it's name but the "term" will be known at programming time.

<snip>

What is it about PHP that forces it to dictate javascript property
names?

John
--
John Harris

[Matt Kruse]

John G Harris wrote:

What is it about PHP that forces it to dictate javascript property
names?

Programmer convenience - if you name an array of checkboxes "input[]" for
example, then they will be automagically converted to an array on the server
side. And the input name is a property or the form.elements[] collection
which is accessed via javascript.

--
Matt Kruse
http://www.JavascriptToolbox.com
http://www.AjaxToolbox.com

[Randy Webb]

John G Harris said the following on 11/19/2006 3:13 PM:

In article <GO************ ********@telcov e.net>, Randy Webb
<Hi************ @aol.comwrites

<snip>

>PHP's array-ness of inputs comes to mind first. If the name of the
inputs is "myInput[]" then you have to use bracket notation to access
it using it's name but the "term" will be known at programming time.

<snip>

What is it about PHP that forces it to dictate javascript property
names?

When form elements are submitted to PHP on the server, any like names
followed by [] are automatically put into a PHP array. As a result, you
see NAME attributes that look like this: 'myInput[]'. It has nothing to
do with dictating javascript property names, it has to do with having to
use bracket notation to access that form element when it is named like that.

--
Randy
Chance Favors The Prepared Mind
comp.lang.javas cript FAQ - http://jibbering.com/faq
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

[Randy Webb]

Dr J R Stockton said the following on 11/19/2006 1:22 PM:

In message <GO************ ********@telcov e.net>, Sat, 18 Nov 2006
19:46:57, Randy Webb <Hi************ @aol.comwrites

>Dr J R Stockton said the following on 11/18/2006 3:44 PM:

<snip>

>>Square bracket notation is necessary if the "term" must be supplied at
run time.

That is not always true. Square bracket notation is necessary if the
"term" has characters in that JS doesn't like. PHP's array-ness of
inputs comes to mind first. If the name of the inputs is "myInput[]"
then you have to use bracket notation to access it using it's name but
the "term" will be known at programming time.

That very specific issue is dealt with in Section 4.25.

When I wrote 'Square bracket notation is necessary if the "term" must be
supplied at run time', I meant 'Square bracket notation is necessary if
the "term" must be supplied at run time'.

And my point is that your statement is false. It implies that is the
only time it is necessary and that isn't true. Perhaps if I had quoted
the previous line to the one I quoted you wouldn't be splitting hairs
about what I wrote. Because the previous line is also patently false.

--
Randy
Chance Favors The Prepared Mind
comp.lang.javas cript FAQ - http://jibbering.com/faq
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

[Dr J R Stockton]

In comp.lang.javas cript message
<sg************ **@jgharris.dem on.co.uk.nospam .invalid>, Sun, 19 Nov 2006
19:58:59, John G Harris <jo**@nospam.de mon.co.ukwrote:

>In article <Y9************ **@invalid.uk.c o.demon.merlyn. invalid>, Dr J R
Stockton <jr*@merlyn.dem on.co.ukwrites

>>Properties can be addressed by dot notation and by square bracket
notation.

Dot notation is appropriate where the "term" is known at programming
time.

Dot notation is not appropriate when the property name does not obey the
rules for identifiers.

Then :
"Dot notation is appropriate where the "term" is an identifier known at
programming time."

>>Square bracket notation is necessary if the "term" must be supplied at
run time.

"term" is pretty woolly. What's wrong with property name? It's explicit
and accurate.

I put it in quotes because something better failed to occur to me at the
time! Though, in the context, "property" might be considered implicit.

To allow for the Merkins, the FAQ should contain, in Section 1, the
observation that "if" does not mean "if and only if"; and the "if"s in
the more rigorous parts of the FAQ should be scrutinised for compliance.

In 4.7, for example, "if" is correct; the condition is sufficient but
not necessary (example : for integer N, (N - N/2 - N/2) is exactly zero,
though if N is 1 then N/2 is non-integer).

But in 4.31 the second "if" should be "whether".

<FAQENTRY>
4.4, 4.10 Subject : if -whether

S.1 para 4 : false.

S.1 para 7 : We use those conventions. "Suggestion s" is undefined. If
the browser supports CSS, then by default one will see ...

In 4.31 the second "if" should be "whether".

--
(c) John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v6.05 MIME.
Web <URL:http://www.merlyn.demo n.co.uk/- FAQish topics, acronyms, & links.
Proper <= 4-line sig. separator as above, a line exactly "-- " (SonOfRFC1036)
Do not Mail News to me. Before a reply, quote with ">" or "" (SonOfRFC1036)

[Randy Webb]

Dr J R Stockton said the following on 11/20/2006 11:50 AM:

<snip>

To allow for the Merkins, the FAQ should contain, in Section 1, the
observation that "if" does not mean "if and only if"; and the "if"s in
the more rigorous parts of the FAQ should be scrutinised for compliance.

And to allow for the anally retentive people among us Section 1 should
contain a note about being anally retentive!

--
Randy
Chance Favors The Prepared Mind
comp.lang.javas cript FAQ - http://jibbering.com/faq
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

[John G Harris]

In article <ej*********@ne ws3.newsguy.com >, Matt Kruse
<ne********@mat tkruse.comwrite s

>John G Harris wrote:

>What is it about PHP that forces it to dictate javascript property
names?

Programmer convenience - if you name an array of checkboxes "input[]" for
example, then they will be automagically converted to an array on the server
side. And the input name is a property or the form.elements[] collection
which is accessed via javascript.

Thank you.

This looks suspiciously like eval to me :-)

John

PS See! It isn't only VK who gets thanked.
--
John Harris

[Dr J R Stockton]

In comp.lang.javas cript message <Oo************ ********@telcov e.net>,
Sun, 19 Nov 2006 18:43:54, Randy Webb <Hi************ @aol.comwrote:

>Dr J R Stockton said the following on 11/19/2006 1:22 PM:

>In message <GO************ ********@telcov e.net>, Sat, 18 Nov 2006
19:46:57, Randy Webb <Hi************ @aol.comwrites

>>Dr J R Stockton said the following on 11/18/2006 3:44 PM:

<snip>

Square bracket notation is necessary if the "term" must be supplied at
run time.

That is not always true. Square bracket notation is necessary if the
"term" has characters in that JS doesn't like. PHP's array-ness of
inputs comes to mind first. If the name of the inputs is "myInput[]"
then you have to use bracket notation to access it using it's name
but the "term" will be known at programming time.

That very specific issue is dealt with in Section 4.25.

When I wrote 'Square bracket notation is necessary if the "term"
must be supplied at run time', I meant 'Square bracket notation is
necessary if the "term" must be supplied at run time'.

And my point is that your statement is false. It implies that is the
only time it is necessary and that isn't true. Perhaps if I had quoted
the previous line to the one I quoted you wouldn't be splitting hairs
about what I wrote. Because the previous line is also patently false.

No : the problem is that not only can you not write English, but also
you cannot even read it.

The word "if" does not mean "if and only if".

My statement quoted at the top is equivalent to

If the "term" must be supplied at run time, then square bracket
notation is necessary.

But, of course, "then" does not mean "then and only then".

Consider "If a person lives in Utah, then he/she is resident in
America.". That's generally believed to be true, even I presume in
Iowa, where dwellers are also American residents.

--
(c) John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v6.05 MIME.
Web <URL:http://www.merlyn.demo n.co.uk/- FAQish topics, acronyms, & links.
For news:borland.*, use their server newsgroups.borl and.com ; but first read
Guidelines <URL:http://www.borland.com/newsgroups/guide.htmlff. with care.

[Randy Webb]

Dr J R Stockton said the following on 11/20/2006 3:50 PM:

In comp.lang.javas cript message <Oo************ ********@telcov e.net>,
Sun, 19 Nov 2006 18:43:54, Randy Webb <Hi************ @aol.comwrote:

>Dr J R Stockton said the following on 11/19/2006 1:22 PM:

>>In message <GO************ ********@telcov e.net>, Sat, 18 Nov 2006
19:46:57, Randy Webb <Hi************ @aol.comwrites
Dr J R Stockton said the following on 11/18/2006 3:44 PM:

<snip>

Square bracket notation is necessary if the "term" must be supplied at
run time.
That is not always true. Square bracket notation is necessary if the
"term" has characters in that JS doesn't like. PHP's array-ness of
inputs comes to mind first. If the name of the inputs is "myInput[]"
then you have to use bracket notation to access it using it's name
but the "term" will be known at programming time.

That very specific issue is dealt with in Section 4.25.
When I wrote 'Square bracket notation is necessary if the "term"
must be supplied at run time', I meant 'Square bracket notation is
necessary if the "term" must be supplied at run time'.

And my point is that your statement is false. It implies that is the
only time it is necessary and that isn't true. Perhaps if I had quoted
the previous line to the one I quoted you wouldn't be splitting hairs
about what I wrote. Because the previous line is also patently false.

I snipped everything you said that made any sense. You are a half wit
sometimes.

--
Randy
Chance Favors The Prepared Mind
comp.lang.javas cript FAQ - http://jibbering.com/faq
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/