What is a Hash in javascript? How can i use a hash for an array?

Question

I'm using an array in my object prototype which basically has add, remove, search functions attached to it.

Something like this

myobj = function() {
  this.Array_ = [];
}

myobj.prototype.add = function(item) {
  goog.array.insert(this.Array_, item);
}

myobj.prototype.hasItem = function(item) {
  goog.array.contains(this.Array_, item);
}

And a sample Array in my case would list of integers. [1, 2, 3, 4]

But later I learnt that this is very costly and can be cost saving if I use hash. Can someone explain use of hash with the above example.

possible duplicate of hashtable in javascript

Sarfraz
– Sarfraz

2012-06-17 08:49:51 +00:00
Commented Jun 17, 2012 at 8:49 — Sarfraz
– Sarfraz, Commented Jun 17, 2012 at 8:49
That sounds like you're using it like you might a set.

Asherah
– Asherah

2012-06-17 09:44:19 +00:00
Commented Jun 17, 2012 at 9:44 — Asherah
– Asherah, Commented Jun 17, 2012 at 9:44
@Sarfraz Solves my question thanks

RaviTeja
– RaviTeja

2012-06-17 11:49:47 +00:00
Commented Jun 17, 2012 at 11:49 — RaviTeja
– RaviTeja, Commented Jun 17, 2012 at 11:49

georg · Accepted Answer · 2013-05-24 22:39:37Z

8

The word "hash" has many meanings, but in this case it probably refers to generic javascript Objects, which are "hashtables" internally. Objects have "add" and "contains" functionality built-in:

foo = {}

foo['x'] = 1   // "add"
'x' in foo     // "contains"

Do note, however, that keys are always converted to strings, therefore if you want keys of other types (e.g. generic objects), you'll have to use custom functions, for example:

contains = function(ary, obj) {
    return ary.indexOf(obj) >= 0;
}

add = function(ary, obj) {
    if (!contains(ary, obj))
        ary.push(obj)
}

edited May 24, 2013 at 22:39

answered Jun 17, 2012 at 9:17

georg

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1 Comment

Jon Onstott Over a year ago

By "there's no way to store an object in a hashtable" you mean "there's no way to store an object as a key in a hashtable"?

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