Trouble with javascript Constructors in multiple files

Question

I am trying to make and test a trie in javascript and have split the nodes, trie and test into separate files. I am using node.js to share the code between files. I have tried messing around with the export and require but keep getting a type error saying that the import is not a constructor.

In trienode.js

function trieNode(val, par) {
  this.value = val;
  this.children = {};
  this.isWord = false;
  this.freq = 0;
  this.parent = par;
}

trieNode.prototype.getValue = function() {
  return this.value;
}

module.exports.tn = trieNode();

In trie.js

var trieNode = require('./trienode.js').tn;

function Trie() {
  console.log('initialize trie');
  console.log(typeof trieNode);
  this.root = new trieNode(null);
  this.saved = {}
  this.current;
}

Trie.prototype.insert = function(word) {
}

Trie.prototype.findSuggestions = function(prefix) {
}
module.exports = Trie();

In test.js

var Trie = require('./trie.js');
var trieNode = require('./trienode.js').tn;

var tr = new Trie();

tr.insert("boot");
tr.insert("boot");
tr.insert("boot");
tr.insert("book");
tr.insert("book");
tr.insert("boom");
var sug = tr.findSuggestions("boo");
for(s in sug) {
  console.log(s);
}

This is the error I'm getting

TypeError: trieNode is not a constructor
    at Trie (C:\Users\agnu\Desktop\autocomplete\trie.js:6:15)
    at Object.<anonymous> (C:\Users\agnu\Desktop\autocomplete\trie.js:94:18)
    at Module._compile (module.js:653:30)
    at Object.Module._extensions..js (module.js:664:10)
    at Module.load (module.js:566:32)
    at tryModuleLoad (module.js:506:12)
    at Function.Module._load (module.js:498:3)
    at Module.require (module.js:597:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (C:\Users\agnu\Desktop\autocomplete\test.js:1:74)

Mark · Accepted Answer · 2018-10-20 18:07:55Z

2

You are exporting the results of the function, not the function itself.

If you want to call the function after importing it, you need to just export the functions:

module.exports.tn = trieNode;

and

module.exports = Trie;

Then, after importing them, you call the functions.

answered Oct 20, 2018 at 18:07

Mark

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3 Comments

Ryan Wilson Over a year ago

I didn't catch this problem, but thanks for the post. Will it work passing one parameter when the constructor expects two?

Mark Over a year ago

@RyanWilson you don't have to pass all arguments to a function. If you don't it will just have the value of undefined in the function.

Ryan Wilson Over a year ago

@MarkMeyer Ah, thanks for clarifying that. I am used to compiler errors in C# if you try to call a constructor with less parameters than the one defined. I'll remove my comment. +1 from me.

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