1. To avoid iterating through the array while adding an item, so that I don't have to check if objects exists(instead of adding a duplicate).
2. To avoid iterating while retrieving or deleting an item

Code:

1. To avoid iterating through the array while adding an item, so that I don't have to check if objects exists(instead of adding a duplicate).
2. To avoid iterating while retrieving or deleting an item.

Why I chose objects to store items over array is,

1. To avoid iterating through the array while adding an item, so that I don't have to check if objects exists(instead of adding a duplicate).

2. To avoid iterating while retrieving or deleting an item

   function isValid(obj) { return (obj != undefined && obj != null && typeof (obj) != 'undefined'); }

   function uniqueCollection() {

    var collection = {};
    var length = 0;
   

   return { removeItem: function (item) { if (isValid(collection[item])) { delete collection[item]; --length; } }, addItem: function (item) { if (!isValid(collection[item])) { collection[item] = item; ++length; } }, getLength: function () { return length; }, clear: function () { collection = {}; length = 0; }, exists: function (item) { if (isValid(collection[item])) { return true; } return false; }, getItems: function () { var items = []; var i = 0; for (var o in collection) { if (collection.hasOwnProperty(o)) { items[i] = o.toString(); i++; } }

        if (i !== length) {
            alert("Error occurred while returning items");
        }
   
        return items;
    }
   

   };//end of object literal

   };//end of function

Why I chose objects to store items over array is:

1. To avoid iterating through the array while adding an item, so that I don't have to check if objects exists(instead of adding a duplicate).
2. To avoid iterating while retrieving or deleting an item

Code:

function isValid(obj) {
    return (obj != undefined && obj != null && typeof (obj) != 'undefined');
}

function uniqueCollection() {
    var collection = {};
    var length = 0;
    return {
        removeItem: function (item) {
            if (isValid(collection[item])) {
                delete collection[item];
                --length;
            }
        },
        addItem: function (item) {
            if (!isValid(collection[item])) {
                collection[item] = item;
                ++length;
            }
        },
        getLength: function () {
            return length;
        },
        clear: function () {
            collection = {};
            length = 0;
        },
        exists: function (item) {
            if (isValid(collection[item])) {
                return true;
            }
            return false;
        },
        getItems: function () {
            var items = [];
            var i = 0;
            for (var o in collection) {
                if (collection.hasOwnProperty(o)) {
                    items[i] = o.toString();
                    i++;
                }
            }

            if (i !== length) {
                alert("Error occurred while returning items");
            }

            return items;
        }

    };//end of object literal

};//end of function

My question is, is this implementation valid? Are there any disadvantage with this implementation?

function isValid(obj) {
            return (obj != undefined && obj != null && typeof (obj) != 'undefined');
        }

function uniqueCollection() {

    var collection = {};
    var length = 0;
return {
    removeItem: function (item) {
        if (isValid(collection[item])) {
            delete collection[item];
            --length;
        }
    },
    addItem: function (item) {
        if (!isValid(collection[item])) {
            collection[item] = item;
            ++length;
        }
    },
    getLength: function () {
        return length;
    },
    clear: function () {
        collection = {};
        length = 0;
    },
    exists: function (item) {
        if (isValid(collection[item])) {
            return true;
        }
        return false;
    },
    getItems: function () {
        var items = [];
        var i = 0;
        for (var o in collection) {
            if (collection.hasOwnProperty(o)) {
                items[i] = o.toString();
                i++;
            }
        }

        if (i !== length) {
            alert("Error occurred while returning items");
        }

        return items;
    }

};//end of object literal

};//end of function

My question is, is this implementation valid? Are there any disadvantage with this implementation over using an array internally to hold the collection items instead of an object?

Why I chose objects to store items over array is,

1. To avoid iterating through the array while adding an item, so that I don't have to check if objects exists(instead of adding a duplicate).

2. To avoid iterating while retrieving or deleting an item

   function isValid(obj) { return (obj != undefined && obj != null && typeof (obj) != 'undefined'); }

   function uniqueCollection() {

    var collection = {};
    var length = 0;
   

   return { removeItem: function (item) { if (isValid(collection[item])) { delete collection[item]; --length; } }, addItem: function (item) { if (!isValid(collection[item])) { collection[item] = item; ++length; } }, getLength: function () { return length; }, clear: function () { collection = {}; length = 0; }, exists: function (item) { if (isValid(collection[item])) { return true; } return false; }, getItems: function () { var items = []; var i = 0; for (var o in collection) { if (collection.hasOwnProperty(o)) { items[i] = o.toString(); i++; } }

        if (i !== length) {
            alert("Error occurred while returning items");
        }
   
        return items;
    }
   

   };//end of object literal

   };//end of function