leafy

Different Tree Implementations

npm install leafy
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browser support

Leafy

leafy is a library of different tree implementations. leafy can be used in both the browser and node.

Why would I need a tree in javascript? I have arrays and objects.

Good question!

The driving reason behind the creation of leafy was the library nools which needed a datastructure that was

  • fast
  • maintained order
  • could have items inserted into it without having to re-sort the entire structure.

This was needed in order to maintain a real time list of rule activations without having to search or sort the actions on insertion.

Often a tree is overkill but when you need one its good to know its out there.

Installation

npm install leafy

Or download the source (minified)

Note leafy depends on declare.js, extended, is-extended, string-extended, and array-extended

Usage

leafy contains the following tree implementations.

options

When creating a tree you can specify a compare function used to sort items as they are inserted or removed.

var tree = new leafy.AVLTree({
   compare : function(a, b){
       var ret = 0;
       if (a.type > b.type) {
           ret = 1;
       } else if (a.type < b.type) {
           ret = -1;
       }
       return ret;
   }
});

By default the tree uses a natural ordering function.

function compare(a, b) {
   var ret = 0;
   if (a > b) {
       return 1;
   } else if (a < b) {
       return -1;
   } else if (!b) {
       return 1;
   }
   return ret;
}

Each tree contains the following functions.

insert

Insert an item into an the tree.

tree.insert("a");
tree.insert("b");
tree.insert("c");
tree.insert("aa");

remove

Remove an item from a tree.

tree.remove("a");
tree.remove("c");

clear

Remove all items from a tree.


tree.insert("a");
tree.insert("b");
tree.insert("c");
tree.insert("aa");

tree.clear();

isEmpty

Returns a boolean indicating if the tree is currently empty.

tree.insert("a");
tree.insert("b");
tree.insert("c");
tree.insert("aa");

tree.isEmpty(); //false

tree.clear();

tree.isEmpty(); //true

contains

Test if a tree contains a particular value.

tree.insert("a");
tree.insert("b");
tree.insert("c");

tree.contains("a"); //true
tree.contains("d"); //false

**`toArray([order=leafy.IN_ORDER]);

Coverts a tree to an array with the values in the order specified, or in order if not specified

tree.insert("a");
tree.insert("b");
tree.insert("c");

tree.toArray(); //["a", "b", "c", "d"]
tree.toArray(leafy.REVERSE_ORDER); //["d", "c", "b", "a"]

forEach(iterator(iterator[, scope[, order=leafy.IN_ORDER]])

Loop through the items in tree.

By default the tree will loop through items in order.

tree.insert("a");
tree.insert("b");
tree.insert("c");
tree.insert("aa");

tree.forEach(function(item, tree){
    console.log(item); //"a", "b", "c", "d" respectively
});

You can loop through a tree in any order you wish by specifying any of the following orders.

  • leafy.REVERSE_ORDER
  • leafy.IN_ORDER
  • leafy.POST_ORDER
  • leafy.PRE_ORDER

tree.forEach(function(item, tree){
    console.log(item); //"d", "c", "b", "a" respectively
}, null, leafy.REVERSE_ORDER);

map(iterator[, scope[, order=leafy.IN_ORDER]])

Map is very similar to the array counter part except that it returns new tree with the mapped values.

//creates a new tree with the returned values "aa", "bb", "cc", "dd"
var mapped = tree.map(function(item, tree){
    return item + item;
});

filter(iterator[, scope[, order=leafy.IN_ORDER]])

Filter is very similar to the array counter part except that it returns new tree with the mapped values.

//creates a new tree with the returned values "a", "b"
var mapped = tree.map(function(item, tree){
    return item === "a" || item === "b";
});

Other iterator methods.

Trees also contains the following array methods that act just like their array counter part.

Note all of these methods accept an order parameter.

  • reduce
  • reduceRight
  • every
  • some

findLessThan(value[, exclusive=true])

Find all values in a tree less than a particular value. If exclusive is set to false then the original value will be included in the resulting array.

tree.insert("a");
tree.insert("b");
tree.insert("c");
tree.insert("d");

tree.findLessThan("d"); //["a", "b", "c"];
tree.findLessThan("d", false); //["a", "b", "c", "d"];

findGreaterThan(value[, exclusive=true])

Find all values in a tree greater than a particular value. If exclusive is set to false then the original value will be included in the resulting array.

tree.insert("a");
tree.insert("b");
tree.insert("c");
tree.insert("d");

tree.findGreaterThan("a"); //["d", "c", "b"];
tree.findGreaterThan("a", false); //["d", "c", "b", "a"];

print()

Prints the current structure of a tree to the console.

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