What does this JavaScript mean?

Question

I am working on a legacy application and all JS seems mystrious to me.
Here is the few mysterious lines which are loaded before all and I don't have any idea what they are doing.

var i2b2 = {sdx:{TypeControllers:{},Master:{_sysData:{}}},events:{},hive:{cfg:{},helpers:{},base_classes:{}},h:{}};  
if (undefined==i2b2.hive) { i2b2.hive = {}; }     
i2b2.hive.tempCellsList = [
        { code: "PM",
          forceLoading: true 
        },
        { code: "ONT"   },
        { code: "CRC"   },
        { code: "WORK"},
        { code: "SHRINE"},
        { code: "PLUGINMGR",
           forceLoading: true,
           forceConfigMsg: { params: [] }
        }
    ];

There are many more var and if statements but they are doing same thing with different variables.
Please help me to solve this mystery.

Answer 1

The first line initialises i2b2 using nested object literals.

var obj = {}; is a shorter way of writing var obj = new Object();

A simple object literal will be

var simpleObject = {
    property1: "Hello",
    property2: "MmmMMm",
    property3: ["mmm", 2, 3, 6, "kkk"],
    method1: function() {
        alert("my method")
    }
};

A nested one will be

var rectangle = {
    upperLeft: {
        x: 2,
        y: 2
    },
    lowerRight: {
        x: 4,
        y: 4
    }
};

Yours is a classic.

var i2b2 = {
    sdx: {
        TypeControllers: {},
        Master: {
            _sysData: {}
        }
    },
    events: {},
    hive: {
        cfg: {},
        helpers: {},
        base_classes: {}
    },
    h: {}
};

The second line should be IMHO

i2b2.hive = i2b2.hive || {};

This just says that if hive is undefined create a new object.

The last lines create a property tempCellsList to the object hive. ( Please note that hive in turn is a property of i2b2 ) Lastly a new array of objects are added to the property tempCellsList