Is there a data structure like the Java Set in JavaScript?

Question

I want to use a data structure in JavaScript that can be used to store number of IDs. I should be able to check if a key already exists in that set, something like Java Sets.

I want to achive same behaviours as follows (this code is in Java):

Set<String> st = new HashSet<String>();
//add elemets

if(st.contains("aks") ){
  //do something
}

I want a JavaScript/dojo equivalent of the above code.

Answer 1

I've written a JavaScript HashSet implementation that does what you want and allows any object to be a member of the set: http://code.google.com/p/jshashtable

However, if you just need to store strings, you could do something more simply by storing set members as property names of a normal Object. For example:

function StringSet() {
    var setObj = {}, val = {};

    this.add = function(str) {
        setObj[str] = val;
    };

    this.contains = function(str) {
        return setObj[str] === val;
    };

    this.remove = function(str) {
        delete setObj[str];
    };

    this.values = function() {
        var values = [];
        for (var i in setObj) {
            if (setObj[i] === val) {
                values.push(i);
            }
        }
        return values;
    };
}

A note about the implementation: val is an object used internally by the StringSet implementation that is unique to each set. Comparing property values of the object whose property names make up the set (setObj) against val eliminates the need for a hasOwnProperty() check and guarantees that only strings that have been added to the set will show up in values.

Example usage:

var set = new StringSet();
set.add("foo");
set.add("bar");

alert(set.contains("foo")); // true
alert(set.contains("baz")); // false

set.values(); // ["foo", "bar"], though not necessarily in that order
set.remove("foo");
set.values(); // ["bar"]