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?

Quentin · Accepted Answer · 2015-06-25 16:16:41Z

5

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 (...) {

answered Jun 25, 2015 at 16:16

Quentin

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1 Comment

Zerok Over a year ago

It worked! I see now it was a silly fail, thank you for the fix. Also, the convention tips are nice, I think I'm adding them.

DynamoBooster · Accepted Answer · 2015-06-25 16:17:39Z

1

Use this instead of structobject

answered Jun 25, 2015 at 16:17

DynamoBooster

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