90

Given

var myHash = new Array();
myHash['key1'] = { Name: 'Object 1' };
myHash['key2'] = { Name: 'Object 2' };
myHash['key3'] = { Name: 'Object 3' };

How do I remove key2, and object 2 from the hash, so that it ends up in a state as if I did:

var myHash = new Array();
myHash['key1'] = { Name: 'Object 1' };
myHash['key3'] = { Name: 'Object 3' };

delete doesn't do what I want;

delete myHash['key2']

simply gives me this:

var myHash = new Array();
myHash['key1'] = { Name: 'Object 1' };
myhash['key2'] = null;
myHash['key3'] = { Name: 'Object 3' };

the only docs I can find on splice and slice deal with integer indexers, which I don't have.

Edit: I also do not know that 'key2' is necessarily in position [1]

UPDATE

OK slight red herring, delete does seem to do what I want on the surface, however, I'm using json2.js to stringify my object to json for pushing back to the server,

after I've deleted, myHash gets serialized as:

[ { Name: 'Object 1' }, null, { Name: 'Object 3' } ]

Is this a bug in json2.js? or is it something I'm doing wrong with delete?

Thanks

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2
  • 3
    What you're doing is adding properties to an object, which is different than adding elements to an array/hash. You're looking for a way to remove a property, more or less. Try delete myHash.key1, as mentioned in other comments. Commented Sep 6, 2009 at 15:35
  • 2
    If it's a hashtable, you should use var myHash = new Object() instead of var myHash = new Array(). Commented Oct 3, 2012 at 17:33

4 Answers 4

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197

You're looking for delete:

delete myhash['key2']

See the Core Javascript Guide

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4 Comments

I thought this was correct, thats why i tried it in the first place. It does seem to work, my problem actually lies in Json.stringify, ill update the question
use the splice function instead. Delete leaves a hole in the array.
Here is the aforementioned splice function btw.
This is not the best option when the changes to myhash should take place in the current scope only. delete may have side effects if variables elsewhere refer to the myhash object.
11

Why do you use new Array(); for hash? You need to use new Object() instead.

And i think you will get what you want.

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3 Comments

I don't like new at all. I prefer var myHash = [];
Or in this case, myHash={}; :-)
I agree. The only thing that an array gives you is a length which doesn't ever work when you change the indexer something other than an int.
6

You say you don't necessarily know that 'key2' is in position [1]. Well, it's not. Position 1 would be occupied by myHash[1].

You're abusing JavaScript arrays, which (like functions) allow key/value hashes. Even though JavaScript allows it, it does not give you facilities to deal with it, as a language designed for associative arrays would. JavaScript's array methods work with the numbered properties only.

The first thing you should do is switch to objects rather than arrays. You don't have a good reason to use an array here rather than an object, so don't do it. If you want to use an array, just number the elements and give up on the idea of hashes. The intent of an array is to hold information which can be indexed into numerically.

You can, of course, put a hash (object) into an array if you like.

myhash[1]={"key1","brightOrangeMonkey"};
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Comments

1

Another option may be this John Resig remove method. can better fit what you need. if you know the index in the array.

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2 Comments

well not having the index is exactly what the question states
Hey @AndrewBullock I have one query I get JSON array Ex: [{\"Countrycode\":\"DE\",\"count\":\"3\"}] but i want to get like[{"DE":"3"}] like this but i don't get this output Please help me

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