jQuery inArray with Hashtable

Question

I'm using a hash table and I'm trying to check for object existence. However I haven't been successful in figuring out how to do this. Could someone help guide me with this. Thanks.

current code.

When clientId equals field id and has item id return true, else add to saved_tokens.

var saved_tokens = {}; 

if ($.inArray(item.id, saved_tokens) == -1) { 
    saved_tokens.push[clientId] = item.id;
}

Note that you can never call functions without parens. Currently you're setting a property on the .push function. — pimvdb
– pimvdb, Commented Mar 5, 2012 at 20:28
Are you trying to check if the key clientId already exists in the object, or if the value item.id already exists? — nnnnnn
– nnnnnn, Commented Mar 5, 2012 at 20:28
I have multiple clientId's that could share the same items. I need to test the clientId to see if it contains an Item, if not add it to the the saved_toekens with the clientId. — Code Junkie
– Code Junkie, Commented Mar 5, 2012 at 20:31

Rob W · Accepted Answer · 2012-03-05 20:26:57Z

5

Don't use jQuery for that. Use pure JavaScript:

if (!saved_tokens.hasOwnProperty(clientId)) { // If clientId is not in the hash
    saved_tokens[clientId] = item.id;
}

.push is an array method. A {} creates an object. Since this object is not an array, it doesn't have any array methods.

edited Mar 5, 2012 at 20:26

answered Mar 5, 2012 at 20:24

Rob W

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2 Comments

Code Junkie Over a year ago

Does this also prevent duplicate item.id's from being added to the hash?

Rob W Over a year ago

@George No. You have two options: 1) Also maintain a hashtable for the item.id, or 2) Loop through all saved_tokens, and check whether the value is (not) equal to item.id.

Jashwant · Accepted Answer · 2012-03-05 20:32:39Z

0

I personally use 'typeof'.

var saved_tokens = {}; 

if (typeof(saved_tokens[clientId]) == 'undefined') { 
    saved_tokens[clientId] = item.id;
}

answered Mar 5, 2012 at 20:32

Jashwant

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7 Comments

nnnnnn Over a year ago

Noting that this doesn't distinguish between whether clientId exists as a key in the object with the value undefined or if clientId doesn't exist as a key at all. if (clientId in saved_tokens) tests if it has been defined as a key (with any value).

Jashwant Over a year ago

@nnnnnn I dont get your comment. Do you mean to say that if clietId having value 'undefined' and clientId doesnt exits both will be true with typeof ?

nnnnnn Over a year ago

Yes. If saved_tokens has a key clientId but the value associated with that key is undefined then typeof will return "undefined" just as it also would if saved_tokens does not have a key clientId at all. If you need to distinguish between those two possibilities then use if (clientId in saved_tokens), or if you need to know if the property is directly set on the object (and not inherited through the prototype chain) use saved_tokens.hasOwnProperty(clientId)

Jashwant Over a year ago

@nnnnnn May be I am getting your answer wrong but this works, jsbin.com/ayocin/2/edit

nnnnnn Over a year ago

Sorry, your link didn't work for me (might be an IE problem). I'm not saying typeof won't work (it does!), I'm saying it doesn't distinguish between the two cases that might cause the expression saved_tokens[clientId] to be undefined - which for some purposes doesn't matter.

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