help with JSON

[SirCodesALot]

Hi All,

Is it possible to create an JSON object from a string? For example

var myArray = new Array(10)

for (var i=0;i<10;i++)
{
myArray.push("{idx:"+i+",val:"+i+"}");
}

var myStrObj = "[" + myArray.join(",") + "]";

var options = {"val1": "test",
"val2" : myStrObj}

I would like val2 to be an array of the values from myArray. is this
possible, or do i have to break it out manually?

Thanks in advance for your suggestions.
-Scott

 

[Peter Michaux]

Hi All,

Is it possible to create an JSON object from a string? For example

var myArray = new Array(10)

for (var i=0;i<10;i++)
{
myArray.push("{idx:"+i+",val:"+i+"}");

}

var myStrObj = "[" + myArray.join(",") + "]";

var options = {"val1": "test",
"val2" : myStrObj}

I would like val2 to be an array of the values from myArray. is this
possible, or do i have to break it out manually?

Hand building JSON is really not a great idea. It is very error
prone.. It is better to build up a JavaScript object and then use a
JSON dumper function

http://www.json.org/json2.js

var options = {val1:"test", val2:[{idx:0, val:0},{idx:1, val:1}]};
JSON.stringify(options);

Peter

 

[Thomas 'PointedEars' Lahn]

Is it possible to create an JSON object from a string?

You really don't mean "JSON object" here. If there would be such a thing,
it would be an object that is referenced by the property with the name
`JSON'. Remember that JSON is a *data exchange format*, not a framework by
itself. The object that results from parsing JSON is a native user-defined
ECMAScript (Object or Array) object.

For example

var myArray = new Array(10)

Passing a number argument in order to initialize the array is unnecessary,
as ECMAScript arrays are of variable length. It is also error-prone, as
implementations differ: in the next-to-worst case you will end up with an
array that has the number value `10' as its first element. Use

var myArray = [];

instead, it can be considered to be safe although not universally supported
(JavaScript 1.3+, JScript 2.0+, ECMAScript 3).

for (var i=0;i<10;i++)
{
myArray.push("{idx:"+i+",val:"+i+"}");
}

Note that Array.prototype.push() requires at least JavaScript 1.2 and, more
important, JScript 5.5. You may want to augment Array.prototype or the
Array object itself with such a method. (If you choose to augment the
Array.prototype object, you should also provide an iterator method that
handles the side-effects of the augmentation.)

<http://PointedEars.de/es-matrix/>

Also, this only works as long as `i' is not an arbitrary string value.

var myStrObj = "[" + myArray.join(",") + "]";

Array objects inherit a toString() method from Array.prototype that returns
a comma-separated string-converted version of their elements (ECMAScript
Edition 3 Final, section 15.4.4.2). This method is called first on implicit
string conversion (ibid., 8.6.2.6). Therefore,

var myStrObj = "[" + myArray + "]";

suffices.

var options = {"val1": "test",
"val2" : myStrObj}

I would like val2 to be an array of the values from myArray. is this
possible, or do i have to break it out manually?

It is possible. Depending on your JSON-capable framework, you can use
either JSON.parse() (e.g. from json2.js or json_parse.js) or simply eval()
to return the respective object reference; the former is safer but probably
slower than the latter.

Please RTFM next time first: <http://json.org/>


PointedEars

 

[SirCodesALot]

Is it possible to create an JSON object from a string?

You really don't mean "JSON object" here.  If there would be such a thing,
it would be an object that is referenced by the property with the name
`JSON'.  Remember that JSON is a *data exchange format*, not a framework by
itself.  The object that results from parsing JSON is a native user-defined
ECMAScript (Object or Array) object.

For example

var myArray = new Array(10)

Passing a number argument in order to initialize the array is unnecessary,
as ECMAScript arrays are of variable length.  It is also error-prone, as
implementations differ: in the next-to-worst case you will end up with an
array that has the number value `10' as its first element.  Use

  var myArray = [];

instead, it can be considered to be safe although not universally supported
(JavaScript 1.3+, JScript 2.0+, ECMAScript 3).

for (var i=0;i<10;i++)
{
   myArray.push("{idx:"+i+",val:"+i+"}");
}

Note that Array.prototype.push() requires at least JavaScript 1.2 and, more
important, JScript 5.5.  You may want to augment Array.prototype or the
Array object itself with such a method.  (If you choose to augment the
Array.prototype object, you should also provide an iterator method that
handles the side-effects of the augmentation.)

<http://PointedEars.de/es-matrix/>

Also, this only works as long as `i' is not an arbitrary string value.

var myStrObj = "[" + myArray.join(",") + "]";

Array objects inherit a toString() method from Array.prototype that returns
a comma-separated string-converted version of their elements (ECMAScript
Edition 3 Final, section 15.4.4.2).  This method is called first on implicit
string conversion (ibid., 8.6.2.6).  Therefore,

  var myStrObj = "[" + myArray + "]";

suffices.

var options = {"val1": "test",
                    "val2" : myStrObj}

I would like val2 to be an array of the values from myArray. is this
possible, or do i have to break it out manually?

It is possible.  Depending on your JSON-capable framework, you can use
either JSON.parse() (e.g. from json2.js or json_parse.js) or simply eval()
to return the respective object reference; the former is safer but probably
slower than the latter.

Please RTFM next time first: <http://json.org/>

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>

Thank you for both for the reply and "schooling". I know how to
proceed now. BTW, I have always loved the "RTFM" reference.