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Thread: object of objects orientation - selector, appendTo(), set attributes ...

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  1. #1
    Join Date
    Nov 2012
    Posts
    8

    object of objects orientation - selector, appendTo(), set attributes ...

    Hello,
    I have following object of objects:
    var xmlObject = {"@attributes":{"id":"3","name":"Cell"},
    "image":"img1.jpg",
    "linkItem":[
    {"@attributes":{"itemType":"reaction","itemId":"1","itemName":"O2 bubble exchange"},"area":[{"@attributes":{"width":"50","height":"250","top":"0","left":"150"}},{"@attributes":{"width":"100"," height":"250","top":"100","left":"150"}}],"point":[{"@attributes":{"top":"200","left":"20"}},{"@attributes":{"top":"20","left":"200"}}]},
    {"@attributes":{"itemType":"entity","itemId":"1","itemName":"CO2"},"area":[{"@attributes":{"width":"100","height":"250","top":"30","left":"250"}},{"@attributes":{"width":"10", "height":"50","top":"300","left":"150"}}],"point":{"@attributes":{"top":"200","left":"200"}}
    }]};

    now the thing is that I dont really understand, how to operate with this kind of object.
    select problem:
    var x = xmlObject.linkItem[itemId = 1]; works fine , but
    var x = xmlObject.linkItem[itemType = "reaction"]; is not working ... %) why ?

    add object to object problem(e.g. area to specified linkItem):
    how to add object to object ? or just changing attributes of existing object in object (e.g. change width of specified area in specified item)?

    I understand objects in javascript, but nested objects are quite different :/

    Thanx a lot for some post

  2. #2
    Join Date
    Aug 2008
    Location
    Sweden
    Posts
    227
    Here's an example how nested objects works:
    Code:
    var object = {
        'attribute1': 'foo',
        'attribute2': 'bar',
        'attribute3': [
            {
                'attr1': 123,
                'attr2': 456
            },
            {
                'attr1': 'abc', // we change this value to "foobar" later
                'attr2': 'def'
            }
        ]
    };
    
    alert(object['attribute2']); // alerts "bar"
    alert(object['attribute3'][0]['attr2']); // alerts 456
    alert(object['attribute3'][1]['attr1']); // alerts "abc"
    
    object['attribute3'][1]['attr1'] = 'foobar';
    alert(object['attribute3'][1]['attr1']); // now alerts "foobar"
    To explain your problem: when you write xmlObject.linkItem[itemId = 1]; two things happen. First, you're assigning the number 1 to the variable itemId, and second, you're accessing xmlObject.linkItem[1] (which works fine because there is an object at index 1 in the xmlObject.linkItem array).

    When you're writing xmlObject.linkItem[itemType = "reaction"]; similar things happen. First, you're assigning the string "reaction" to the variable itemType, and second, you're accessing xmlObject.linkItem["reaction"]. However, the array xmlObject.linkItem does not have a reaction attribute, so you get 'undefined' back from that expression.

    I hope that clarifies what happens.

    Also note that the following two lines does the same thing - it's only two ways of writing it:
    Code:
    object['attribute1'] = 'hello';
    object.attribute1 = 'hello';
    Code:
    alert(object['attribute1']);
    alert(object.attribute1);
    Last edited by ReFreezed; 12-10-2012 at 06:28 PM.

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