Associative array versus object in JavaScript

Question

In my script there is a need to create a hash table, and I searched in google for this. Most of the folks are recommending JavaScript object for this purpose. The The problem is some of the keys in the hash table have a "." in them. I am able to create these keys easily with the associative arrays.

I don't understand why associative arrays are bad. The first thing that is mentioned on the sites that I looked at is the length property.

I am coming from the Perl background, where I used hashes. Most common uses were to get the value from a key, check if a key exists, delete a key-value pair, and add a key-value pair. If these are my common uses, can I safely use an associative array?

Answer 1

In JavaScript, objects are associative arrays...there aren't separate concepts for them. You are also able to safely use '.' in a key name, but you can only access the value using the bracket notation:

var foo = {} foo['bar'] = 'test'; foo['baz.bin'] = 'value';  alert(foo.bar); // Shows 'test' alert(foo['baz.bin']); // Shows 'value' 

If you're using them already and they work, you're safe.

Answer 2

In a JavaScript, an object and array are pretty much the same thing, with an array having a bit of magical functionality (autoupdating the length property and such) and prototype methods suitable for arrays. It is also much easier to construct an object than using an associative array:

var obj = {"my.key": "myValue"}; 

vs.

var obj = []; obj["my.key"] = "myValue"; 

Therefore never use the array object for this, but just the regular object.

Some functionality:

var obj = {}; // Initialized empty object 

Delete a key-value pair:

delete obj[key]; 

Check if a key exists:

key in obj; 

Get the key value:

obj[key]; 

Add a key-value pair:

obj[key] = value;