hawkharris hawkharris - 1 year ago 94
Javascript Question

Dynamically assigning properties to a JavaScript object (trie)

I'm trying to implement a variation of a trie in JavaScript. Basically, it's an efficient data storage object in which the characters in keys are not repeated. In other words, if I have the keys "abe" and "ann," only one instance of the shared letter "a" should appear:

a: {
b: {
e: {
0: 'lincoln'
n: {
n: {
0: 'mcgee'

Here is the desired implementation and a few usage examples:

function Trie () {
// The top level of the trie.
var root = {};

return {
write: function (key, value) {
read: function (key) {

// Sample usage
var trie = new Trie();

trie.write('abe', 'lincoln');
trie.write('ann', 'mcgee');

trie.read('abe'); // returns 'lincoln'
trie.read('ann'); // returns 'mcgee'

I've run into a blocker with respect to the
method. Given a string key such as "abe," I need to assign a property to
. I can't find a way to assign a value to an object property several layers deep when the number of keys and the values of the keys are unknown.

The only solution that comes to mind is, I think, a bad one: placing the path to the value into a string and using
. For example:
eval("root['a']['b']['e'] = 'lincoln'");

Is there a better solution for dynamically assigning the values? (I realize that this is a bit of complicated problem, so I'm happy to clarify by providing extra information.)

mpm mpm
Answer Source

a very naive approach (given the requirements,though i would write a different implementation)

given a string of keys and a pointer to the root,and a value to assign;

function write(root,path,value){
    var a = path.split(''); // 'abc'->['a','b','c']
    var pointer = root;
    var i=0;
        if(pointer[a[i]] == undefined){
        pointer = pointer[a[i]];
    return root;

EDIT : i'm assuming all the keys exist on their respective object. I added a if condition in case some keys are not defined.

EDIT:2 split corrected, correcting a little bug right now ;)

EDIT:3 should work now.

usage : write({},'abc',1) // yields {a:{b:{c:1}}}
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