Array in Node.js, how to work with it

Question

I'm a newbye in web programming and even more in Javascript, but I'm trying to learn it as I learn Node.js, and I found this strange error... I've got this code:

var structobject = function(type, title, isReplicable, isVisible) {
    this._type = type;
    this._title = title;
    this._childElements = new Array();
    this._isReplicable = isReplicable;
    this._id = 0;  //TODO
};

structobject.prototype.addChild = function (element) {
    structobject._childElements.push(element);
};

structobject.prototype.stringify = function () {
    console.log("Main element: "+this._title);
    for (var i=0;i<this._childElements.length;i++) {
        console.log("Child "+i+": "+this._childElements[i]._title);
    }
};

structo1 = new structobject(1, "element1", true, true);
structo1.addChild(new structobject(2, "element2", true, true));
structo1.stringify();

I've got a problem here... as you may see, _childElements is intended to be an array, and I've got the function addchild which should add a child element into it.

The rest of the code works, but this gives me the following error:

C:\Zerok\DevCenter\Structify\public_html\js\object.js:22
  structobject._childElements.push(element);
                             ^
TypeError: Cannot read property 'push' of undefined

Why does it say childElements is not defined? I tried not defining the variable, and also tried equaling it to this._childElements = []; but none of these ways seem to work either.

What should I do so I can work dynamically with this array?

Answer 1

structobject._childElements.push(element);

You're trying to modify the (non-existent) _childElements property of the Constructor function instead of the instance you created with new structobject .

Use this instead of structobject on that line.

---

It is conventional, in JavaScript, to use variables starting with capital letters for constructor functions.

var structobject = function(...) {

would be better written as:

var Structobject = function(...) {

or (since it is a constructor that makes objects):

var Struct = function(...) {

or (because named functions are easier to deal with in debuggers):

function Struct (...) {

Answer 2

用它代替structobject