How do I index by multiple items in an Array or Object using JavaScript/jQuery?

Question

Background

I have an Array of data in a result object returned by an Ajax call. The data looks like this:

{ Name="User1 Name1", FirstName="User1", Id="005400000001234567", more...}
{ Name="User2 Name1", FirstName="User2", Id="005400000001234568", more...}

Where each item looks like this:

{
    Id:"005400000001234567",
    Name:"User Name",
    FirstName:"User",
    LastName:"Name",
    Title:"Manager"
}

Question

I want to be able to retrieve data either by Id (returning a single user) or by Title (returning an array of users). What would be the best way to go about doing that using JavaScript or jQuery?

Example

Here's what I've attempted so far:

function GetAllUsers()
{
    AllUsersById = new Object();

    MyClass.MyAjaxMethod(function(result,event) {
        if(result) { 
            j$(result).each(function(index,item)
            {
                AllUsersById[item.Id] = item;
            });
        }
    });
}

The code I have above is great for indexing by Id, but I'm not sure what to do for Title.

Additional Details

Also, by the way, there are about 1000 records, and I need this to be fairly efficient. (This is one of the reasons I'm getting the data right away, when the document is ready. I'm not an expert on JavaScript or jQuery efficiency, though. Let me know if you have a better way.)

Any ideas? Thanks in advance!

do you need this to be all one array, or could you build two - one for index by #, one for grouped by title. — circusdei
– circusdei, Commented Feb 14, 2012 at 20:34

sinemetu1 · Accepted Answer · 2012-02-14 20:41:37Z

5

Seems like you're looking for .grep(). Using .grep you could create a generic function that would filter:

function findInJson (json, key, value) {
    return $.grep(json, function (obj) {
        return obj[key] == value;
    });
}

// With your data getting a specific user by id
findInJson(yourJSON, "Id", "005400000001234567");

// Getting a set of users by title
findInJson(yourJSON, "Title", "Manager");

answered Feb 14, 2012 at 20:41

sinemetu1

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2 Comments

Matt K Over a year ago

I noticed in the jQuery reference "The $.grep() method removes items from an array as necessary so that all remaining items pass a provided test." Does grep actually modify the array it's searching through?

sinemetu1 Over a year ago

@MatthewKeefe grep will not change the object that you're searching through.

Anurag · Accepted Answer · 2012-02-14 22:24:31Z

2

Create a constructor function vis-à-vis class that encapsulates this data, and you can ask it to find users by title, or id. To do a quick lookup, you can create two lookup tables - one for id, and another for title. Assuming a decent hash implementation, the lookups can be done in O(1) on the average. The initial computation is O(n), but lookups are faster. Also it uses slightly more space because we are creating two additional maps. For 1000 objects, that is not a problem. Again, if you will be doing a lot more lookups, this approach will be much faster.

Here's a simple implementation.

function Users(users) {
    this.idMap = {};
    this.titleMap = {};
    this.users = users;
    var me = this;

    users.forEach(function(user) {
        this.idMap[user.Id] = this.idMap[user.Id] || [];
        this.idMap[user.Id].push(user);

        this.titleMap[user.Title] = this.titleMap[user.Title] || [];
        this.titleMap[user.Title].push(user);
    }.bind(this));
}

Users.prototype.findByTitle = function(title) {
    return this.titleMap[title];
};

Users.prototype.findById = function(id) {
    return this.idMap[id];
};

To use it, create an object of Users passing it the AJAX response, and then query it using the findById and findByTitle methods.

var users = new Users(responseData);
users.findById("1");
users.findByTitle("SomeTitle");

Checkout a working example.

edited Feb 14, 2012 at 22:24

answered Feb 14, 2012 at 20:58

Anurag

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1 Comment

Matt K Over a year ago

Fascinating. I learned a ton from your answer and example, thanks! However, I think I'll have to go with grep for simplicity.

Diego · Accepted Answer · 2012-02-14 20:59:55Z

If you have control over the data returned, it's better if you produce it with the following format:

var allUsers=[
{"005400000001234567":{
    Name:"User Name",
    FirstName:"User",
    LastName:"Name",`
    Title:"Manager"
}} 
,{"005400000001234568":{
    Name:"User2 Name2",
    FirstName:"User2",
    LastName:"Name2",
    Title:"Manager2"
}} 
/*..etc.. */
];

This way you avoid the loop ($(result).each()) inside GetAllUsers (which builds the array above). The search by title can be performed efficiently by building a second array of the form:

var byTitle=["title1":[0,1], "title1":[0,1], /*etc*/];

As you see, each title has a list of indexes to allUsers. Then you simply do:

var allManagers = [];
for(var i in byTitle["Manager"]) allManagers.push(allUsers[i]);

circusdei · Accepted Answer · 2012-02-14 21:06:42Z

0

I think this should work. I really can't test it without your data.

function GetAllUsers()
{

AllUsersById = new Object();
AllUsersByType = new Object();

MyClass.MyAjaxMethod(function(result,event) {
    if(result) { 
        j$(result).each(function(index,item)
        {
            // By Id
            AllUsersById[item.Id] = item;

            // By Type
            if (!AllUsersByTitle[item.Title]) {
                AllUsersByTitle[item.Title] = new Array();
            }

            AllUsersByType[item.type].push() = item;
        });


    }
});
}

edited Feb 14, 2012 at 21:06

answered Feb 14, 2012 at 20:44

circusdei

1,96712 silver badges29 bronze badges

1 Comment

Matt K Over a year ago

Your first example worked when I grouped it all together in the first each loop and added: if (!AllUsersByTitle[item.Title]) { AllUsersByTitle[item.Title] = new Array(); } before the push.

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