What is the "=>" operator? - firefox

In this link from MDN, it explains how to write a unit test for developing an addon for firefox. However, there are several segments that I don't understand and didn't find any useful result after searching google.
The first one, the following is a paragraph quoted from above link:
In a web page, you can perform Base64 encoding and decoding using the
btoa() and atob() functions. Unfortunately these functions are
attached to the window object: since this object is not available in
your main add-on code, atob() and btoa() aren't available either. So
we'll create a base64 module to expose these functions from the
platform (see Creating Reusable Modules).
What does "the platform" in the above paragraph mean? the "Services.jsm"?
Also in the following code:
const { atob, btoa } = require("resource://gre/modules/Services.jsm");
this makes atob and btoa as one of the Services that is available for other class? or make (constant variables)atob and btoa both reference to the Services.jsm?
The Second one:
what are these two lines of code do?
exports.atob = a => atob(a);
exports.btoa = b => btoa(b);
I understand the part
exports.atob
which enables atob function to be available from other classes outside the "base64.js".
but what does the following mean?
= a => atob(a);
I didn't find that javascript has "=>" operator!
From my understaning, the reason we create a base64.js is because atob and btoa can only be called if we have the window object. Therefore we can use Services.jsm to get a reference of the window object?

For "platform" in the paragraph you quoted they mean the set of functions which is not strictly Firefox browser code but rather implements basic, share functionalities. This usually lives in toolkit/modules in the mozilla-central repository. Services.jsm lives there as well so yes, that's part of the platform. Moreover, atob and btoa are both imported from Services.jsm.
The arrow => in exports.atob = a => atob(a); defines what's called an arrow function: it's a new, shorter syntax to define functions in JavaScript. This SO answer has many useful informations about it.
From my understanding, the reason we create a base64.js is because atob and btoa can only be called if we have the window object. Therefore we can use Services.jsm to get a reference of the window object?
That's almost correct: you need to export the function from the underlying platform as you don't have a window object there. If you had a window object, you would have just done window.atob or something like that. That call would have still called the same function you imported from Services.jsm.
So you're not using Services.jsm to get a reference to the window object, but rather directly importing the needed functions so that you don't need to have a window object.

Related

Omnet/Inet : how to access class/submodules to get variables values

in my simulation there is a mobile node composed by the following components from the inet framework:
Now I am working on the UdpApp which is UDPVideoStreamCli.cc which is also given by inet framework as one of example udp application.
Now as you can see from the image I had to access to the lisp module (which is an instance of LispRouting.cc) because I have to read some values or call some public methods of that class...how can I do that? All I know is that I have to start from
getParentModule()->getSubmodule();
but then I don't know how to go on...can you help?
(LispRouting *)getParentModule()->getSubmodule("lisp")
will do the trick. Be sure to check if the returned pointer is not null.
Generally this is bad design as it hard-codes the name and the relative position of the LispRouting module. Any change in naming/architecture will cause crashes.
A proper design would be to create a parameter that specifies the name/path of the lisp submodule (with default value) and then use
#include "inet/common/ModuleAccess.h"
...
LispRouting *lr = getModuleFromPar<LispRouting>(par("lispModule"), this);
and then add a parameter to the module's NED file:
string lispModule = default("^.lisp");
meaning the default place where you can find the lisp module is: go one level up and then find the submodule named "lisp". This is a much better pattern, because the user can later reconfigure the name/placement of the lisp module without breaking the code.

Invoke Method with client.soda ( Statement Object Model )

I am trying to build Esper EPL statements in Java.
I use the com.espertech.esper.client.soda lib for this, but I can't find
a tutorial to help me.
The PatternExpressions are the only part that I need as of now.
As an example let's use the EPL:
every a=Event((a).getEventTypeCode()='E00001')
So he should trigger on every Event with the event type code E00001, we get the code by
calling the getEventTypeCode Method.
How do I project this to SOM?
With:
PatternExpr pattern = Patterns.everyFilter("Event","a");
I only get:
every a=Event
(of course)
I know there is a class called "MethodInvocationStream" but I don't know how to use it.
And I cannot find examples for its use.
Thanks to user650839 I found out how to add Methods via SOM.
Here is a simple EPL as an SOM Object: http://imgur.com/SDrTsa7
One source of info is the javadoc.
You could simply do the reverse and compile EPL text to a model object and inspect that. Use "epAdmin.compileEPL", the output is the same object you want to build via API.\

How can I pass a local variable from function to event listener function in JavaScript?

Good day!
I began writing my own basic JavaScript library for personal use and distribution a few days ago, but I am having trouble with one of the methods, specifically bind().
Within the method itself, this refers to the library, the object.
I went to Google and found function.call(), but it didn't work out the way I planned it--it just executed the function.
If you take a look at another method, each(), you'll see that it uses call() to pass values.
I also tried the following:
f.arguments[0]=this;
My console throws an error, saying it cannot read '0' of "undefined".
I would like to be able to pass this (referencing the library--NOT THE WINDOW) to use it in the event listener.
You can see it starting at line 195 of the JavaScript of this JSFiddle.
Here it is as well:
bind:function(e,f){
if(e.indexOf("on")==0){
e=e.replace("on","");
}
if(typeof f==='function'){
/*Right now, 'this' refers to the library
How can I pass the library to the upcoming eventListener?
*/
//f=f(this); doesn't work
//f.call(this); //doesn't work
//this.target refers to the HTMLElement Object itself, which we are adding the eventListener to
//the outcome I'm looking for is something like this:
/*$('h3').which(0).bind(function({
this.css("color:red");
});*/
//(which() defines which H3 element we're dealing with
//bind is to add an event listener
this.target.addEventListener(e,f,false)
}
return this;
},
Thank you so much for your help, contributors!
If, as per your comments, you don't want to use .bind(), rather than directly passing f to addEventListener() you could pass another function that in turn calls f with .call() or .apply():
if(typeof f==='function'){
var _this = this;
this.target.addEventListener(e,function(event){
f.call(_this, event);
},false)
}
Doing it this way also lets your library do any extra event admin, e.g., pre-processing on the event object to normalise properties that are different for different browsers.
So in this particular case you actually want to call JavaScript's built in bind method that all functions have.
f = f.bind(this);
f will be a new function with it's this argument set to whatever you passed into it.
Replace f=f(this); with f.apply(this);
Look at underscore code, here:
https://github.com/jashkenas/underscore/blob/master/underscore.js#L596

Microsoft AJAX: Unable to get property 'x' of undefined or null reference

How do I troubleshoot the following error being thrown by a Microsoft AJAX JavaScript framework method? It is an automatically generated line of JavaScript from a custom User Control in a Web Forms App (Sitefinity 5 CMS)
Error Message:
Unable to get property 'FancyBlockDesigner' of undefined or null reference
Here is the JavaScript that is throwing the error:
Sys.Application.add_init(function() {
$create(SitefinityWebApp.Esd.TheLab.SampleHtmlEditor.FancyBlockDesigner, null, null, {"Editor":"propertyEditor_ctl00_ctl00_ctl00_ctl00_ctl00_Editor","propertyEditor":"propertyEditor"}, $get("propertyEditor_ctl00_ctl00_ctl00"));
});
Rather than discuss the ascx and cs files that try to abstract this detail away from me, I want to know what this error means. If I understand the detail, the abstraction might make more sense.
"$create" function in ASP.NET Ajax creates an instance of JavaScript class. Microsoft had their own opinion on how to make JavaScript object orientated and as time had shown, their approach wasn't exactly perfect.
Anyhow, to try to explain what is happening, let me give a bit of an overview oh how it works. We start by a server side control which implements IScriptControl interface which mandates two members: GetScriptDescriptors and GetScriptReferences. The second one is pretty straightforward - it lets you register references to all JavaScript files that you control will require. The GetScriptDescriptors, on the other hand, let's you define all the instances of JavaScript classes you want to use as well as it lets you set their properties - initialize them, if you will.
What the autogenerated JavaScript code you've pasted says is basically that you have defined in GetScriptDescriptors that you will need an instance of type "SitefinityWebApp.Esd.TheLab.SampleHtmlEditor.FancyBlockDesigner" where you want Editor property to be initialized. This code will go and look for a JavaScript constructor that looks like this:
function SitefinityWebApp.Esd.TheLab.SampleHtmlEditor.FancyBlockDesigner(element) {
}
that most probably also has a prototype defined, something like:
SitefinityWebApp.Esd.TheLab.SampleHtmlEditor.FancyBlockDesigner.prototype = {
}
Now, since the error you have posted states: "Unable to get property 'FancyBlockDesigner' of undefined or null reference", most probably one of the following is the problem:
You have not included the JavaScript file which contains the class (constructor + prototype) that I've talked about above
You have forgot to add the "FancyBlockDesigner" to the constructor (it seems that you do have other object, perhaps through MS Ajax namespaces - "SitefinityWebApp.Esd.TheLab"
You have not registerd the "SampleHtmlEditor" namespace. Make sure at the top of your JS file you have this: Type.registerNamespace("SitefinityWebApp.Esd.TheLab.SampleHtmlEditor");
So, short story long, the function with name "SitefinityWebApp.Esd.TheLab.SampleHtmlEditor.FancyBlockDesigner" cannot be found.
Hope this helps,
Ivan

Interactively execute code while debugging in Scala

Is there a method for inserting code into a Scala application while debugging? For example, could I have something like this,
var c = 1.0
0.until(10).foreach{ i =>
if (i == 5) {
startDebuggingMagicHere()
}
}
where I could then inspect and interact with c, i, and any other variable in scope via methods and assignment.
In the Scala-IDE plugin for Eclipse, debugging is supported. Set a breakpoint in the Scala code and you will be able to do limited things. Current support is not as good as that for Java. I believe it is planned to improve by the Summer.
What you can do is:
use the "variables" view to see the current values of variables and modify values,
tell the debugger to "drop to frame" so that it starts the current method call again, using the original values from the stack,
modify code and save the file which causes the debugger to insert the new code and drop to frame, i.e. restart the method call (this does not always work - depending how much you change the code you may need to restart the app, e.g. if you change the class definition)
What you can't do is:
inspect variables from the editor,
write code in the "display" view and execute it. Both of these work with Java, but not Scala.

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