I'm using Node JS and ExpressJS to write my web server. I use JavaScript OOP fromfew time. I get an error running this class:
class myClass {
constructor(path) {
this.path = path;
}
myFunction(){
var fileControllerInstance = new FileController(this.path);
fileControllerInstance.fileExist(function(fileExist) {
if(fileExist){
console.log("file exist");
this.printLine("test");
}
else
return false;
});
}
printSTR(str){
console.log(str);
}
}
new myClass("filePath").myFunction();
module.exports = myClass;
Running this class I get an error on printSTR function. Error is the follow:
file exist
TypeError: Cannot read properties of undefined (reading 'printSTR')
Without this I get ReferenceError: printSTR is not defined. To solve my problem I need to create another class instance and to use that to call the function. Something like this:
new myClass("filePath").printSTR("test") instead to ``` this.printLine("test"); ```
Why using this my code not working? Thanks
Inside the function(fileExist), this has a different value than outside. To inherit the value inside, you must bind the function:
fileControllerInstance.fileExist(function(fileExist) {
...
}.bind(this));
You're calling this inside a callback. You can find this post useful to solve your issue.
Also you try to call printLine("test") but your method is printSTR(str)
Related
I'm trying to figure out how to use the browser-based aws-sdk.js with require.js when building a web app.
If I try to build a class and include aws-sdk in the require.js define, once I try to create an instance and reference the AWS class, it says it is undefined.
For example, I have a function that checks to see if the credentials are an instance of AWS.Credentials and if not, it tries to initialize it with an STS token it retrieves via Rest.
The problem is, the code dies on the if(this.credentials instanceof AWS.Credentials) saying AWS is undefined. It even dies on my simple check of the needsRefresh.
This is what my define looks like - I'll include the 'needsRefresh' wrapper for an example of the sort of thing that is throwing the Undefined error:
define(['require','aws-sdk','jquery'],
function (require, AWS, $) {
// Aws helper class
function AwsHelper() { };
AwsHelper.prototype = {
credentials: null,
tokenNeedsRefresh: function () {
//////////////////////////////////////////////////////////////////
// errors out on the following line with: //
// TypeError: Cannot read property 'Credentials' of undefined //
//////////////////////////////////////////////////////////////////
if(this.credentials instanceof AWS.Credentials) {
return this.credentials.needsRefresh();
} else return true;
}
};
return AwsHelper;
}
);
I also tried the following format at the top of the file:
define(function (require) {
var AWS = require("aws-sdk"),
$ = require("jquery");
/* .. */
If I remove all onLoad references to the refresh code running, it will load and I can create an instance. But as soon as I call any function that references the AWS class, it dies.
How do I make sure that AWS class definition is still in global space once an instance is spawned?
Dunno what difference the paths will make (it's finding and loading the code just fine - I can see AWS Class in namespace in the debugger as it's loading but it's not in the namespace on the function call), but added on request:
requirejs.config({
baseUrl: '/js',
paths: {
lib: 'lib',
ImageUploader: 'ImageUploader'
}
});
I decided to try to play with this again and seemed to have figured out how I was going about it incorrectly. I have yet to integrate it back into my existing code setup, but I think I have a working solution.
The thing I was doing wrong was I was trying to set up the AWS class so I could load it as a module (thus why I tried wrapping it as the require.js suggested).
Playing with it this time around, I noticed something I hadn't before. I had an AWS that was undefined in the local scope and an other AWS that held the class definition in the global scope. So it was trying to specify AWS in my define that was creating the local 'null' version:
define(
["jquery","aws-sdk","dropzone","app/MyUtilities"],
function ($, AWS, Dropzone, MyUtilities) {
"use strict";
function MyClass() {};
return MyClass;
}
);
jquery and dropzone have whatever is needed to make sure they load that way, but aws-sdk seems to do some of it's own asynchronous loading. Thus the scope variable in the function is undefined.
Technically, it seems the only thing I needed defined as a module in the function wrapper is my own utilities module. So by switching it to:
define(
["app/MyUtilities","jquery","aws-sdk","dropzone"],
function (MyUtilities) {
"use strict";
function MyClass() {};
return MyClass;
}
);
... it seems $ and jquery are defined as needed, Dropzone is defined as needed and AWS is defined as needed. (and I don't get my errors when accessing the static AWS.config or AWS.Credentials definitions as I did before)
I'm getting an error when trying to stringify a global variable in sails:
TypeError: converting circular structure to JSON.
I know what the error means, but the question is, what's happening that's causing there to be a circular reference. And, why does it happen to my custom variable?
Then the next question is: how can I stringify the object the way I created it in globals.js?
In config/globals.js:
module.exports.globals = {
mystuff: {
Url: "http://localhost:8080",
APIKey: "2bb67717b99a37e92e59003f93625c9b"
}
}
In a hook initialize:
module.exports = function (sails) {
return {
initialize: function(cb) {
var str = JSON.stringify(sails.config.globals.mystuff);
}
}
}
This helped identify circular culprits:
Detecting and fixing circular references in JavaScript
Another portion of the app was injecting objects into the globals.
I can't figure out why I get an undefined here for 'app':
module.exports = {
application: require('../../app').service,
request: require('supertest')(this.application),
startSetup: setup(this.application)
};
it throws up at the (this.application) for the request: line.
Yo can try this:
var app = require('../../app').service;
module.exports = {
application: app,
request: require('supertest')(app),
startSetup: setup(app)
};
The problems is that this.application doesn't exists yet.
You can't use the inside parts of an object that it is not defined (it is defined only after the final }).
Here is an example that you can try on your chrome console.
You can see that you can't use type because it is not defined.
Javascript doesn't know what this.application is. The object hasn't been defined yet so you can't use an attribute inside at object definition that's defined in the same object.
I am trying to keep my code separated in modules. When I defined my first module I extended sap.ui.base.Object and it worked. My question is: Is it a must to extend sap.ui.base.Object when defining my own module? According to the API documentation I tried following example:
sap.ui.define([], function() {
// create a new class
var SomeClass = function();
// add methods to its prototype
SomeClass.prototype.foo = function() {
return "Foo";
}
// return the class as module value
return SomeClass;
});
I required this module inside my Component.js as dependency like this:
sap.ui.define([
"path/to/SomeClass"
], function (SomeClass) {
"use strict";
//var test = new SomeClass();
I always receive a syntax error:
failed to load '[...]/Component.js' from ./Component.js: Error: failed to load '[...]/module/SomeClass.js' from ./module/Service.js: SyntaxError: Unexpected token ;
Does anyone have an idea why this happens? Thanks!
We group code in modules like this for example:
jQuery.sap.declare("our.namespace.iscool.util.Navigation");
our.namespace.iscool.util.Navigation = {
to: function (pageId, context) {
// code here
}
// etc.
}
and call the function of the module like this in a controller
jQuery.sap.require("our.namespace.iscool.util.Navigation");
sap.ui.controller("our.namespace.iscool.Detail", {
// somewhere in this file comes this
handleNavButtonPress: function (evt) {
our.namespace.iscool.util.Navigation.navBackToMaster(
evt.getSource().getBindingContext()
);
},
}
Stupid mistake - missing curly brackets in the docs.
var someclass = function() {} ;
As an experiment, I'm trying some stuff out with dart and easyrtc. I started at porting this (it is normally served through a nodejs server, found here) to a dart version and this is what I made from it
EDIT: I found out which part of the code is causing the error. It is the data object proxy which the for loop is unable to run through. Normally, the setRoomOccupantListener function gives as parameters the name of the room and an object with all the peers connected to the room. I have made a screenshot of the object layout in normal javascript as how it looks when I debug in chrome, found here.
function connect() {
easyrtc.setRoomOccupantListener(convertListToButtons);
}
function convertListToButtons (roomName, data, isPrimary) {
clearConnectList();
var otherClientDiv = document.getElementById("otherClients");
for(var easyrtcid in data) {
var button = document.createElement("button");
button.onclick = function(easyrtcid) {
return function() {
performCall(easyrtcid);
};
}(easyrtcid);
var label = document.createTextNode(easyrtc.idToName(easyrtcid));
button.appendChild(label);
otherClientDiv.appendChild(button);
}
}
And here is the screenshot when i debug the dart code in chromium
void connect() {
easyrtc.setRoomOccupantListener(convertListToButtons);
}
void convertListToButtons(roomName, data, isPrimary) {
clearConnectList();
var otherClientDiv = querySelector("#otherClients");
for (var easyrtcid in data) {
var button = document.createElement("button");
button.onClick.listen((event) {
performCall(easyrtcid);
});
button.appendText(easyrtc.idToName(easyrtcid));
otherClientDiv.append(button);
}
}
This is the error I get:
Class 'Proxy' has no instance getter 'iterator'.
NoSuchMethodError: method not found: 'iterator' Receiver: Instance of 'Proxy' Arguments: []
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:45)
#1 P...<omitted>...7)
Am I missing something simple here or is this some kind of incompatibility? Thank you.
I see you can use import package:js/js.dart'; too. I don't know how to use it
You could try
import 'dart:js' as js;
https://www.dartlang.org/articles/js-dart-interop/
This looks weird too
easyrtc = js.context.easyrtc; // <== here you have context 'easyrtc'
easyrtc.easyApp('easyrtc.audioVideo', 'selfVideo', new js.JsObject.jsify(['callerVideo']), loginSuccess, loginFailure);
// and here again 'easyrtc.audioVideo', I guess this is one to much
try
easyrtc.easyApp.callMethod('audioVideo', ['selfVideo', js.JsObject.jsify(['callerVideo']), loginSuccess, loginFailure]);
where 'audioVideo' is the called method and the rest are arguments
easyrtc.callMethod('easyApp', ['audioVideo', 'selfVideo', js.JsObject.jsify(['callerVideo']), loginSuccess, loginFailure]);
where 'easyApp' is the called method and the rest are arguments.
If you can add how the code would look in JavaScript I could create better examples.
Like dart:js package:js doesn't handle directly Dart List. So the following line :
easyrtc.easyApp('easyrtc.audioVideo', 'selfVideo',
['callerVideo'], loginSuccess, loginFailure);
should be :
easyrtc.easyApp('easyrtc.audioVideo', 'selfVideo',
js.array(['callerVideo']), loginSuccess, loginFailure);
See also What is a difference between dart:js and js package?