Explicit declaration of array type required?

[d.adamkiewicz]

Hello Folks

I was wondering if the following could be better written:

var myObject = {};
/*
in this case explicit declaration seems to be mandatory
otherwise 'myObject.ala has no properties' error occurs
*/
if (typeof myObject["ala"] == "undefined") {
myObject["ala"] = [];
}

myObject["ala"].push("ela");

Regards
Darek

[Thomas 'PointedEars' Lahn]

d.***********@i7.com.pl wrote:

I was wondering if the following could be better written:

var myObject = {};
/*
in this case explicit declaration seems to be mandatory
otherwise 'myObject.ala has no properties' error occurs
*/

Of course, `undefined' has no properties.

if (typeof myObject["ala"] == "undefined") {
myObject["ala"] = [];
}

This condition is only necessary if the "ala" property is running the risk
of not being defined or explicitly assigned `undefined' before.

myObject["ala"].push("ela");

Backwards compatible:

var myObject = new Object();
myObject.ala = new Array("ela");

or (ECMAScript 3 compliant):

var myObject = {ala: ["ela"]};
PointedEars
--
"Use any version of Microsoft Frontpage to create your site. (This won't
prevent people from viewing your source, but no one will want to steal it.)"
-- from <http://www.vortex-webdesign.com/help/hidesource.htm>

[jim]

var myObject = {ala: []};
myObject.ala.push("ela");

could also do:

window.myObject={
ala:[],
alb:{a:1,b:"two",c:[3]},
alc: (false)? true:false,
ald: "hello"
};

cheers, Jim

[Thomas 'PointedEars' Lahn]

Thomas 'PointedEars' Lahn wrote:

d.***********@i7.com.pl wrote:

>if (typeof myObject["ala"] == "undefined") {
myObject["ala"] = [];
}

This condition is only necessary if the "ala" property is running the risk
of not being defined or explicitly assigned `undefined' before.

Clarification: It is not necessary at all, unless a specific program
behavior is attached to its having the value `undefined'.

myObject["ala"] = [];

creates the property and/or assigns a (new) value to it.
PointedEars
--
"Use any version of Microsoft Frontpage to create your site. (This won't
prevent people from viewing your source, but no one will want to steal it.)"
-- from <http://www.vortex-webdesign.com/help/hidesource.htm>

[Thomas 'PointedEars' Lahn]

jim wrote:

var myObject = {ala: []};

^^^^^^^^^^^^^^

myObject.ala.push("ela");

could also do:

window.myObject={

^^^^^^^^^^^^^^^^

ala:[],
alb:{a:1,b:"two",c:[3]},
alc: (false)? true:false,
ald: "hello"
};

Those two assignments are in no way equivalent.
PointedEars
--
var bugRiddenCrashPronePieceOfJunk = (
navigator.userAgent.indexOf('MSIE 5') != -1
&& navigator.userAgent.indexOf('Mac') != -1
) // Plone, register_function.js:16

[Randy Webb]

Thomas 'PointedEars' Lahn said the following on 8/6/2007 4:01 AM:

jim wrote:

>var myObject = {ala: []};

^^^^^^^^^^^^^^

>myObject.ala.push("ela");

could also do:

window.myObject={

^^^^^^^^^^^^^^^^

>ala:[],
alb:{a:1,b:"two",c:[3]},
alc: (false)? true:false,
ald: "hello"
};

Those two assignments are in no way equivalent.

And the phrase "could also do" indicates it as an alternative, not as an
equivalent.

--
Randy
Chance Favors The Prepared Mind
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