Does JQuery support Dictionaries (key, value) collection?

Question

Does JQuery support Dictionaries (key, value) collection ?

I would like to set the following data in a structure

[1, false]
[2, true]
[3, false]

with the ability to add, lookup, delete and update.

Any help!

While Javascript supports a dictionary-type of collection, why not just store the values in an array since your keys are numerical? — kevmo314, Mar 23 '11 at 07:49
Do you need to store the data with respect to a DOM element or in general.Why cant you use a simple javascript object.If the data needs to be stored with respect to particular DOM elements you could check out http://api.jquery.com/jQuery.data/ — frictionlesspulley, Mar 23 '11 at 07:50
Storing the required structure is possible with Javascript's `JSON`, as an array of objects (`[[1, false],[2, true],[3, false]]`) or with key, value association (`[{"id": 1, "enabled": false},{"id": 2, "enabled": true},{"id": 1, "enabled": false}]`). But I'm not sure there are in-built methods for manipulation. — Amil Waduwawara, Mar 23 '11 at 07:54
I haven't known that I can do that with Javascript. I'm a beginner. Thanks a lot. — Homam, Mar 23 '11 at 08:12
@AmilWaduwawara: Why use JSON for that? JSON is a string. I don't think that is what the OP wants. JavaScript objects are good enough and JS object !== JSON. — Felix Kling, Mar 23 '11 at 08:13
@John: Reading a tutorial is never wrong: https://developer.mozilla.org/en/JavaScript/Guide — Felix Kling, Mar 23 '11 at 08:14
@Amil Waduwawara: JSON is a text format for representing objects, and it's not part of Javascript but based on Javascript syntax. I think that you mean an *object literal*. If you use the keys as keys instead of values, there are built-in methods for manipulations, otherwise you have to loop the array to manipulate it. — Guffa, Mar 23 '11 at 09:01

score 116 · Accepted Answer · answered Mar 23 '11 at 07:50

116

No, jQuery doesn't, but Javascript does.

Just use an object:

var dict = {
  "1" : false,
  "2" : true,
  "3" : false
};

// lookup:
var second = dict["2"];
// update:
dict["2"] = false;
// add:
dict["4"] = true;
// delete:
delete dict["2"];

answered Mar 23 '11 at 07:50

Guffa

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Thanks a lot. small question: Can I initialize it with no values ? – Homam Mar 23 '11 at 08:14
6

@John: Yes, just omit the values: `var dict = {};`. – Felix Kling Mar 23 '11 at 08:15
You should think about updating the answer to include `map` - would be really helpful for the future. (even though such answers shouldn't become the single point of truth, aka a manual) – Mar 06 '16 at 21:00
1

This is not `hasOwnProperty` safe. – Peter Mar 08 '16 at 22:33
@AndreasNiedermair: What do you mean by map? – Guffa Mar 08 '16 at 22:42
@Peter: What do you mean by "hasOwnProperty safe"? – Guffa Mar 08 '16 at 22:44
If someone were to look for a key named `hasOwnProperty` it would return `Object.prototype.hasOwnProperty`. Furthermore, if this property was overwritten, then code invoking `dict.hasOwnProperty()` would fail. – Peter Mar 08 '16 at 22:48
1

@Guffa, basically this is a flaw with JavaScript. The only way around this is to wrap the object and with safe dictionary API to get and set key/values. `map` is an ES6 solution. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map – Peter Mar 08 '16 at 23:03
What would be the syntax for adding a new entry in `dict` for an already existing key? Considering I want to add `"2" : "false"` to `var dict = { "1" : false, "2" : true, "3" : false };` – user1928158 Jul 08 '16 at 09:02
1

@user1928158: It's not possible to have duplicate keys in an object. They key `"2"` can only have a single value, so setting it will overwrite the previous value. If you need multiple values for keys then consider using arrays as values, i.e. `{ "1" : [ false ], "2": [ true, false ], "3" : [ false ] }`. That of course involves more code for using and manipulating the object. Another alternative would be to use an array of objects, e.g. `[ { key: "1", value: false }, { key: "2", value: true }, { key: "2", value: false }, { key: "3", value: false }, ]`. – Guffa Jul 12 '16 at 09:54
how to recuparate `myDict.Keys`? – serge Jan 15 '19 at 15:33

Felix Kling · Answer 2 · 2011-03-23T08:17:28.017

6

jQuery, no. But JavaScript does. There are only two structures in JavaScript, arrays and objects.

Objects can be used as dictionary, where the properties are the "keys":

var dict = {
    1: true,
    2: true,
    3: false
};

Properties of objects can be either accessed with dot notation, obj.property (if the property name is a valid identifier, which a digit as used above is not) or with array access notation, obj['property'].

edited Mar 23 '11 at 08:17

answered Mar 23 '11 at 07:50

Felix Kling

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don't you think since `console.log(dict.1)` is impossible to write it is very confusing, espacially on cases like: `var foo = {3: true, 2: true, 1: false}; console.log(foo[1]);` – Caspar Kleijne Mar 23 '11 at 08:14
@CasparKleijne: Not really sure *what* you think is confusing. You mean it could be confused with an array? Imo one should always know which data structure one is dealing with. – Felix Kling Mar 23 '11 at 08:19
What would be the syntax for adding a new entry in `dict` for an already existing key? Considering I want to add `"2" : "false"` to `var dict = { "1" : false, "2" : true, "3" : false };` – user1928158 Jul 08 '16 at 09:05

score 3 · Answer 3 · answered Mar 23 '11 at 07:49

You don't need separate dictionary classes, since Javascript objects act as dictionaries. See this:

var userObject = {}; // equivalent to new Object()
userObject["lastLoginTime"] = new Date();
alert(userObject["lastLoginTime"]);

Full article here: http://msdn.microsoft.com/en-us/magazine/cc163419.aspx

score 3 · Answer 4 · answered Mar 23 '11 at 07:50

3

With pure JavaScript,

var myDictionary = new Object();
myDictionary[1] = false;
myDictionary[2] = true;
myDictionary[3] = false;

function look(i) { return myDictionary[i];}
look(1); // will return false

answered Mar 23 '11 at 07:50

Mithun Sreedharan

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score 2 · Answer 5 · answered Mar 23 '11 at 07:48

2

Yes, you can use object to do this:

var myDict = { 1:false , 2:true , 3:false };

answered Mar 23 '11 at 07:48

Benoît

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What would be the syntax for adding a new entry in `dict` for an already existing key? Considering I want to add `"2" : "false"` to `var dict = { "1" : false, "2" : true, "3" : false };` – user1928158 Jul 08 '16 at 09:04

Does JQuery support Dictionaries (key, value) collection?

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