Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Ordered Hash Map
/*
* Simple hash map using javascript objects and an ordered array.
* Repeated elements are not allowed.
*
* @param sort_method By default is ASC order, but you can specified whatever you want.
*
* The public methods are:
* -set
* -get
* -del
* -foreach
* next step: Try to improve the insert method
*/
var HashMap = function (sort_method){
var data = {};
var order_keys = [];
var default_sort = function(a,b) {
return a < b;
};
var sort = sort_method || default_sort;
/*
* Insert the new key using the sort method.
*/
function insert(key) {
var len = order_keys.length;
if (len == 0) {
order_keys.push(key);
} else {
for (i = 0; i < len; i++) {
if (sort(key, order_keys[i])) {
if (order_keys[i-1] != key) { /* the element is not repeated */
order_keys.splice(i,0, key);
}
break;
}
}
if ( i== len) {
order_keys.splice(i,0, key);
}
}
}
function binarySearch(a, value, low, high) {
if (high < low)
return -1 // not found
mid = parseInt(low + (high - low) / 2)
if (a[mid] > value)
return binarySearch(a, value, low, mid-1)
else if (a[mid] < value)
return binarySearch(a, value, mid+1, high)
else
return mid // found
}
function del(key) {
delete data[key];
var index = binarySearch(order_keys, key, 0, order_keys.length);
if (index > -1) order_keys.splice(index,1);
}
function set(key, value) {
data[key] = value;
insert(key);
}
function get(key) {
return data[key];
}
/*
* Executes a specified function on each ordered element of the array;
* Stop if the callback returns false
*/
function foreach(callback) {
var len = order_keys.length;
for (var i = 0; i < len; i++) {
if (callback(order_keys[i], data[order_keys[i]]) === false) break;
}
}
return {set:set, get:get, foreach:foreach, del:del};
}
@luwes

This comment has been minimized.

Copy link

commented May 9, 2017

The insert function has a bug which would add repeated elements. This fixes it.

            if (i === len) {
                if (order_keys[i - 1] !== key) { /* the element is not repeated */
                    order_keys.splice(i, 0, key);
                }
            }
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.