javascript - Elminating duplicates in a JSON object

Question

[
  {
    "lastName": "Seymour",
    "gender": "Female",
    "patientID": 18134,
    "firstName": "Stephanie",
    "age": "111Y"
  },
  {
    "lastName": "Seymour",
    "gender": "Female",
    "patientID": 18134,
    "firstName": "Stephanie",
    "age": "111Y"
  }
]

How can i check my json before adding whether it contains this value or not...

Answer 1

Obvious way

The most obvious way would be to use a for loop and iterate over all items in array and compare every time when you'd like to know whether you already have a particular item in it. Trivial but tedious especially when you have many compares to make.

function contains(items, obj) {
    var itemKey = null;
    var objKey = obj.firstName + ";" + obj.lastName;
    var result = false;
    for(var i = 0; !result && i < arr.length; i++)
    {
        itemKey = items[i].firstName + ";" + items[i].lastName;
        result = itemKey === objKey;
    }
    return result;
};

Whenever you'd be searching for existing object:

contains(arr, newObj);

Smart(er) way

This code uses the ability of Javascript whose prototypes can be used as arrays in a sort of associative memory storage. Suppose you have your JSON items in arr variable. Define your compare key (say it's first name and last name):

var arr = /* your JSON object */;
var hash = (function() {
    var keys = {};
    return {
        contains: function(key) {
            return keys[key] === true;
        },
        add: function(key) {
            if (keys[key] !== true)
            {
                keys[key] = true;
            }
        }
    };
})();

var key = null;
for (var i = 0; i < arr.length; i++)
{
    key = arr[i].firstName + ";" + arr[i].lastName;
    if (!hash.contains(key))
    {
        hash.add(key);
    }
}

Finding out whether you already have an item in your array is then pretty simple:

hash.contains(key);

And that's it. Much faster than iterating over the whole array. Especially when it has many items.