How do I make a JSON object with multiple arrays?

On the outermost level, a JSON object starts with a { and end with a }.

Sample data:

{
    "cars": {
        "Nissan": [
            {"model":"Sentra", "doors":4},
            {"model":"Maxima", "doors":4},
            {"model":"Skyline", "doors":2}
        ],
        "Ford": [
            {"model":"Taurus", "doors":4},
            {"model":"Escort", "doors":4}
        ]
    }
}

If the JSON is assigned to a variable called data, then accessing it would be like the following:

data.cars['Nissan'][0].model   // Sentra
data.cars['Nissan'][1].model   // Maxima
data.cars['Nissan'][2].doors   // 2

for (var make in data.cars) {
    for (var i = 0; i < data.cars[make].length; i++) {
        var model = data.cars[make][i].model;
        var doors = data.cars[make][i].doors;
        alert(make + ', ' + model + ', ' + doors);
    }
}

Another approach (using an associative array for car models rather than an indexed array):

{
    "cars": {
        "Nissan": {
            "Sentra": {"doors":4, "transmission":"automatic"},
            "Maxima": {"doors":4, "transmission":"automatic"}
        },
        "Ford": {
            "Taurus": {"doors":4, "transmission":"automatic"},
            "Escort": {"doors":4, "transmission":"automatic"}
        }
    }
}

data.cars['Nissan']['Sentra'].doors   // 4
data.cars['Nissan']['Maxima'].doors   // 4
data.cars['Nissan']['Maxima'].transmission   // automatic

for (var make in data.cars) {
    for (var model in data.cars[make]) {
        var doors = data.cars[make][model].doors;
        alert(make + ', ' + model + ', ' + doors);
    }
}

Edit:

Correction: A JSON object starts with { and ends with }, but it's also valid to have a JSON array (on the outermost level), that starts with [ and ends with ].

Also, significant syntax errors in the original JSON data have been corrected: All key names in a JSON object must be in double quotes, and all string values in a JSON object or a JSON array must be in double quotes as well.

See:

  • JSON specification
  • JSONLint - The JSON validator

Another example:

[  
[  
    {  
        "@id":1,
        "deviceId":1,
        "typeOfDevice":"1",
        "state":"1",
        "assigned":true
    },
    {  
        "@id":2,
        "deviceId":3,
        "typeOfDevice":"3",
        "state":"Excelent",
        "assigned":true
    },
    {  
        "@id":3,
        "deviceId":4,
        "typeOfDevice":"júuna",
        "state":"Excelent",
        "assigned":true
    },
    {  
        "@id":4,
        "deviceId":5,
        "typeOfDevice":"nffjnff",
        "state":"Regular",
        "assigned":true
    },
    {  
        "@id":5,
        "deviceId":6,
        "typeOfDevice":"44",
        "state":"Excelent",
        "assigned":true
    },
    {  
        "@id":6,
        "deviceId":7,
        "typeOfDevice":"rr",
        "state":"Excelent",
        "assigned":true
    },
    {  
        "@id":7,
        "deviceId":8,
        "typeOfDevice":"j",
        "state":"Excelent",
        "assigned":true
    },
    {  
        "@id":8,
        "deviceId":9,
        "typeOfDevice":"55",
        "state":"Excelent",
        "assigned":true
    },
    {  
        "@id":9,
        "deviceId":10,
        "typeOfDevice":"5",
        "state":"Excelent",
        "assigned":true
    },
    {  
        "@id":10,
        "deviceId":11,
        "typeOfDevice":"5",
        "state":"Excelent",
        "assigned":true
    }
],
1
]

Read the array's

$.each(data[0], function(i, item) {
         data[0][i].deviceId + data[0][i].typeOfDevice  + data[0][i].state +  data[0][i].assigned 
    });

Use http://www.jsoneditoronline.org/ to understand the JSON code better


A good book I'm reading: Professional JavaScript for Web Developers by Nicholas C. Zakas 3rd Edition has the following information regarding JSON Syntax:

"JSON Syntax allows the representation of three types of values".

Regarding the one you're interested in, Arrays it says:

"Arrays are represented in JSON using array literal notation from JavaScript. For example, this is an array in JavaScript:

var values = [25, "hi", true];

You can represent this same array in JSON using a similar syntax:

[25, "hi", true]

Note the absence of a variable or a semicolon. Arrays and objects can be used together to represent more complex collections of data, such as:

{
    "books":
              [
                {
                    "title": "Professional JavaScript",
                    "authors": [
                        "Nicholas C. Zakas"
                    ],
                    "edition": 3,
                    "year": 2011
                },
                {
                    "title": "Professional JavaScript",
                    "authors": [
                        "Nicholas C.Zakas"
                    ],
                    "edition": 2,
                    "year": 2009
                },
                {
                    "title": "Professional Ajax",
                    "authors": [
                        "Nicholas C. Zakas",
                        "Jeremy McPeak",
                        "Joe Fawcett"
                    ],
                    "edition": 2,
                    "year": 2008
                }
              ]
}

This Array contains a number of objects representing books, Each object has several keys, one of which is "authors", which is another array. Objects and arrays are typically top-level parts of a JSON data structure (even though this is not required) and can be used to create a large number of data structures."

To serialize (convert) a JavaScript object into a JSON string you can use the JSON object stringify() method. For the example from Mark Linus answer:

var cars = [{
    color: 'gray',
    model: '1',
    nOfDoors: 4
    },
    {
    color: 'yellow',
    model: '2',
    nOfDoors: 4
}];

cars is now a JavaScript object. To convert it into a JSON object you could do:

var jsonCars = JSON.stringify(cars);

Which yields:

"[{"color":"gray","model":"1","nOfDoors":4},{"color":"yellow","model":"2","nOfDoors":4}]"

To do the opposite, convert a JSON object into a JavaScript object (this is called parsing), you would use the parse() method. Search for those terms if you need more information... or get the book, it has many examples.

Tags:

Json

Recent Posts