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up vote 1 down vote favorite

Is it possible to make access to a property of an object into an array of objects like a matrix?

I mean something like this:

jSon generated object:

[
    {
        "Nome": "1",
        "Departamento": "1",
        "Cargo": "1"
    },
    {
        "Nome": "5",
        "Departamento": "5",
        "Cargo": "5"
    },
    {
        "Nome": "2",
        "Departamento": "2",
        "Cargo": "2"
    },
    {
        "Nome": "3",
        "Departamento": "33",
        "Cargo": "33"
    },
    {
        "Nome": "4",
        "Departamento": "4",
        "Cargo": "4"
    }
]

How I'm trying access the object properties:

object[0][1] = value;

What I already do:

object[0]["Nome"] = value;

I've searched a lot, but I can't find a solution for this problem.

share|improve this question
1  
You can't access an object's property in the same way you do an array's index (which is what it appears you're trying to do). If you need to use indexes to access the values, I'd suggest converting those objects to arrays. –  M Sost Jun 26 '13 at 16:41
    
How can I do this conversion? Can I convert the array into a matrix and then back to an array of objects? –  Wellington Zanelli Jun 26 '13 at 16:42
1  
@Wellington: What do you need the matrix for? What should happen to the property names (they're not included in the matrix so converting back is complicated)? In what order do you want the items' values to be, currently the objects are unordered? –  Bergi Jun 26 '13 at 16:46
1  
If you do need to do the conversion, you can do it with something like this: jsbin.com/aruhud/2/edit –  M Sost Jun 26 '13 at 16:49
1  
@Wellington: But you don't need a matrix for that, your current structure is totally fine. Of course, a CSV-like structure with additional header information (and column order) would work as well, yet it is not required. –  Bergi Jun 26 '13 at 17:02
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2 Answers

up vote 2 down vote accepted

No.

Objects and Arrays are two very different types in JavaScript. In an Array order is very important but order is not retained for Object keys. Keep in mind you can still iterate over the keys of an Object.

for (var prop in myObj) {
  console.log("myObj.prop -> ", myObj[prop]);
}
share|improve this answer
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up vote 2 down vote

As already stated, Arrays and Objects are different. I don't really follow your reasoning for converting from one structure to the other, and you should probably consider working in a different way, which is totally possible from your question and comment descriptions. But, if you really must convert then you will need to perform some kind of mapping, to and from, to be sure that things are ordered correctly. You could do something like this.

Javascript

function toMapped (array) {
    var mapping = {
            "Nome": 0,
            "Departamento": 1,
            "Cargo": 2
        },
        mapped = [],
        length = array.length,
        i = 0,
        element,
        j;

    while (i < length ) {
        element = [];

        for (j in mapping) {
            if (mapping.hasOwnProperty(j) && array[i].hasOwnProperty(j)) {
                element[mapping[j]] = array[i][j];
            }
        }

        mapped.push(element);
        i += 1;
    }

    return mapped;
}

function fromMapped (array) {
    var mapping = {
            0: "Nome",
            1: "Departamento",
            2: "Cargo"
        },
        mapped = [],
        length = array.length,
        i = 0,
        object,
        j;

    while (i < length ) {
        object = {};
        for (j in mapping) {
            if (mapping.hasOwnProperty(j) && array[i].hasOwnProperty(j)) {
                object[mapping[j]] = array[i][j];
            }
        }

        mapped.push(object);
        i += 1;
    }

    return mapped;
}

var test = [{
    "Nome": "1",
    "Departamento": "1",
    "Cargo": "1"
}, {
    "Nome": "5",
    "Departamento": "5",
    "Cargo": "5"
}, {
    "Nome": "2",
    "Departamento": "2",
    "Cargo": "2"
}, {
    "Nome": "3",
    "Departamento": "33",
    "Cargo": "33"
}, {
    "Nome": "4",
    "Departamento": "4",
    "Cargo": "4"
}];

var mapped = toMapped(test);
var unmapped = fromMapped(mapped);

console.log(test);
console.log(mapped);
console.log(unmapped);

On jsfiddle

Using ECMA5 Array.prototype.map

Javascript

function toMapped(array) {
    var mapping = {
        "Nome": 0,
        "Departamento": 1,
        "Cargo": 2
    };

    return array.map(function (object) {
        var element = [],
            i;

        for (i in mapping) {
            if (mapping.hasOwnProperty(i) && object.hasOwnProperty(i)) {
                element[mapping[i]] = object[i];
            }
        }

        return element;
    });
}

function fromMapped(array) {
    var mapping = {
        0: "Nome",
        1: "Departamento",
        2: "Cargo"
    };

    return array.map(function (element) {
        var object = {},
            i;

        for (i in mapping) {
            if (mapping.hasOwnProperty(i) && element.hasOwnProperty(i)) {
                object[mapping[i]] = element[i];
            }
        }

        return object;
    });
}

var test = [{
    "Nome": "1",
        "Departamento": "1",
        "Cargo": "1"
}, {
    "Nome": "5",
        "Departamento": "5",
        "Cargo": "5"
}, {
    "Nome": "2",
        "Departamento": "2",
        "Cargo": "2"
}, {
    "Nome": "3",
        "Departamento": "33",
        "Cargo": "33"
}, {
    "Nome": "4",
        "Departamento": "4",
        "Cargo": "4"
}];

var mapped = toMapped(test);
var unmapped = fromMapped(mapped);

console.log(test);
console.log(mapped);
console.log(unmapped);

On jsfiddle

share|improve this answer
1  
I'd recommend to just iterate/enumerate over the mapping instead of the object/subarray. Also, you really really should use the map function instead of forEach… –  Bergi Jun 26 '13 at 18:45
    
Of course it can be done in many ways, I would normally have used while, for cross-browser compatibility in such examples, but was a little lazy/short of time so used forEach. But sure map would also have been appropriate for ECMA5 methods. –  Xotic750 Jun 26 '13 at 19:07
    
@Bergi Updated with your suggestions. –  Xotic750 Jun 26 '13 at 20:00
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