scala.js call external js function - javascript

I want to try using scala.js on a SalesForce project.
SalesForce automatically injects the Visualforce.remoting.Manager.invokeAction(...) function to enable querying data and doing dml.
How can I call this function from scala.js?

In the crudest sense, you could just invoke it directly from global scope using js.Dynamic, something like:
js.Dynamic.global.Visualforce.remoting.Manager.invokeAction(...)
That works for a one-off, but if you're going to be working more with this Manager, I'd probably recommend creating a Scala.js facade for the Manager, and assigning the Manager object to that -- it'll probably result in better code in the long run.

You should be able to call any exposed javascript method from scala-js using
scala.scalajs.js.eval(x: String)
Example for calling a bootbox modal:
import scala.scalajs.js.annotation.JSExportTopLevel
import scala.scalajs.js
#JSExportTopLevel("myCallBack")
protected def confirmCallback() = // do stuff
def askAQuestion(): Unit = {
js.eval("bootbox.confirm(\"Your question goes here.\", function(result) { if (result == true) { myCallBack(); }});")
}
Of course for this to work you have to include the javascript libary in your project.
Since this is a quite messy solution, you might consider writing your own facade.

Related

How do you use multple files in a JavaScript project that will not be used as a web application? Need a single working example

I'm kind of going nuts here.
I need to start writing a stand alone non web application in JavaScript.
My problem is that I can run (using nodejs) the script just fine, but I can't split the code that I need to write among multiple files because then I don't know how to include them.
Rigth now all I want is the simplest working example of including a JS file inside another so I can use the functions defined there (or class if I so choose).
My test.js looks like this.
const { outputText } = require("./text_module.node.js");
outputText();
While my text_module.node.js looks like this:
function outputText(){
console.log("hello world");
}
My package.json looks like this:
{
"type": "text_module.node.js"
}
I have tried
Adding export before the function. It tells me export is unexpected
Using this notation: import { something } from "a_path". Anything that uses this notation will get me an "Unexpected token {" error.
The current configuration simply tells me that outputText() is not a function. So I'm out of ideas.
I don't know how else to search. I've been searching for hours on this topic and it seem that no matter where I look there is some HTML code that is needed to tie everything togeter or using another third party tool. Using jQuery loads stuff "asynchronically" which is not what I need. I want it to sequential.
Is JS just NOT suppossed to be used like other scripting languages? Otherwise I can't figure out why this is so complicated. I feel like I'm missing something big here.
If you want to use const { outputText } = require("./text_module.node.js");,
export it as module.exports = { outputText: outputText }.
In your question,
Adding export before the function. It tells me export is unexpected
Because it's an es6 thing and nodejs doesn't support all es6 features. You can refer to this answer for more details on that.

Calling Java function from Rhino

Calling Javascript functions running inside Rhino from Java is easy enough - that after all is why Rhino was created. The thing I am having trouble establishing is this:
Context: I have a Phonegap CLI (v 6.3.3) Android project (API 19+) where I do a great deal of processing via loadable JavaScript running inside rhino
A Phonegap plugin - which I am creating at the same time as the actual Phonegap app - contains class called Storage which provides public, static, methods such as readFromFile(String fileName), writeToFile(String fileName,String data) etc.
What I want to be able to do is to call Storage.readFromFile etc from my loaded JavaScript code in Rhino.
Just how this should be done is not too clear to me. From the searches I have done thus far it involves using ScriptableObject.putProperty to pass the Java class in question, Storage in my case to JavaScript. However, how this should be done and then how it should be used at the JS end leaves me rather confused.
I would be most grateful to anyone here who might be able to point me in the right direction
Given that Rhino has less than 100 followers here it should perhaps come as little surprise that this question was not answered. In the mean time I have managed to find the solution myself and it turns out to be very simple. I share it below for the benefit of anyone else running into this thread.
My Storage class is very simple. It goes something like this
public class Storage
{
public static boolean haveFile(){}
public static boolean readFromFile(String fname){}
...
}
When I call Javascript from Java via Rhino I simply pass a new instance of the Storage class as the last of my function parameters
Context rhino = Context.enter();
Object[] functionParams = new Object[] {"Other parameters",new Storage()};
rhino.setOptimizationLevel(-1);
try
{
Scriptable scope = rhino.initStandardObjects();
String rhinoLog = "var log = Packages.io.vec.ScriptAPI.log;";
String code = /*Javascript code here* as shown separately below/;
rhino.evaluateString(scope, rhinoLog + code, "ScriptAPI", 1, null);
Function function = (Function) scope.get("jsFunction", scope);
Object jsResult = function.call(rhino,scope,scope,functionParams);
}
where the Javascript code is
function jsFunction(a,s)
{
//a - or a,b,c etc - here will be the "other" parameters
//s - will be the instance of the Java side Storage class passed above
//now you can do things like
s.writeToFile('fileName','fileData');
var fd = s.readFromFile('fileName');
s.dropFile('fileName');
...
}

Architecture for creating a JavaScript framework

Around one year ago we started a web system that over the time has grown quite a bit. From the beginning the goal was to build reusable code that would speed up the development of future projects, and it has. With every new project, the reusable code from the previous was taken and build upon it.
At the moment, the server side code is really clean, and there is a clear separation between the "framework" (generic functionality) and the project specific logic.
However, the javascript has grown out of control. For the page specific javascript (button events, ajax calls, etc.) we've been using closures and the module pattern. But the javascript common files (the ones we import in every page), are full of functions with no association between them beyond some similarities on the names.
Because of this I'm now trying to build a sort of framework (easily reusable and maintainable code) encapsulating the logic and functions we already have. It should be one "core" object and several optional "extensions". They would be in separate files to improve the order of the code. Specifically, I'm trying to achieve the following:
Encapsulation of the code to prevent name collisions. We are very comfortable with the private/public separation of the closures.
Extendable functionality, something like the open/close principle. The tricky part here is that an extension might want to access a private method of the core.
I've been reading a lot on OO in javascript, and I've even tried to understand how jQuery does it, but I'm still unable to get my head around it. For the architectural side, it seems that I should be building a module or service framework, but the ones I've found are much more complex than what I want to achieve.
If it weren't for the tricky part mentioned earlier, a simple $.extension() would do, but I'm stuck in the how to access a core private method from an extension part. In short, my question would be: Is there a recommended architecture in javascript to build something like the following example?
var framework = function () {
//Private variable
var internalState = 1;
//Private method
var validState = function () { ... }
//Public methods
return {
commonTask1: function () { ... },
commonTask2: function () { ... }
}
}();
framework.addMoreFunctionality(function () {
var specificData = '';
return {
extensionMethod: function () {
//TRICKY PART HERE
if (core.validState()) { ... }
}
}
}());
Just return a function from the framework module.
return {
isValidState: function() { ... }
commonTask1: function () { ... },
commonTask2: function () { ... }
}
The isValidState function could then check the internal state.
// isValidState
function() {
if (validState()) {
return true;
}
return false;
}
Check if the state is valid then by calling core.isValidState(); Like this you will not get any reference to any "private" variable inside the framework core because the functions returns a bool and not a direct reference to any objects.
Have you explored DOJO ? It has module system, a build system and very elaborate OO framework implemented.
You can have your own modules / "base Dijits" that will help you implement "generic modules/widgets" and then extend them per-project, by writing / adding specific capabilities the way you have described.
DOJO is not exactly in Vogue, but if your application deals with forms like interface, then it's definitely a candidate.

Use of prototype for single instance functions in JavaScript

For performance optimization I'm using a single JavaScript file to handle all the pages of the website I'm working on.
The basic structure I'm using is as followed:
(function($) {
// Shared functions ...
// A function for every page
function Page1() {
}
Page1.prototype = {
init: function() {
//...
},
//more functions
};
// more pages
$(document).ready(function() {
if ($('#page1uniqueidentifier').length) {
var page1 = new Page1();
page1.init();
}
// more pages
}
}) (jQuery);
I'm not an experienced JavaScript programmer so I've been searching a lot about best practices and different ways of structuring my code and I've ended up choosing this one but I'm not really sure about it and I have a few questions:
Is it worth it to use prototype if I'm never gonna have more than a single instance of a page? I think I understand how prototype works and that I'm not gaining any performance there. But I'm using it just as a best practice because in the case different instances would exist, these functions would be the same in every instance.
Is there a better way to structure the code?
Should I put the call of the init function inside the constructor and then only call new Page1()?
function Page1() {
this.init();
}
if ($('#page1uniqueidentifier').length) {
new Page1();
}
For performance optimization I'm using a single JavaScript file to
handle all the pages of the website I'm working on
That makes no sense. You should separate code into files, and then run all your js files thru a minimizer/concatenator to package it up.
Anyway, to answer your questions,
if you are only going to have 1, then prototype won't buy you anything. However, if you are going to use more than 1, would you go back and change it? Plus, using prototype wont hurt you either, so you might as well do it for learning.
You should create the files that make sense according to the functionality implemented. I would separate your object definition into its own file, for example, so when you look at that file, all you see is the code for that object.
If you have a constructor function, you don't really need init, do you?

Use Javascript to call method within a flash (.swf) file?

I have a flash file that contains a package "game" which has a class "Scores" and a method setValue(). I want to write some lines of Javascript that allow me to call that method. Someone directed me to this tutorial, but I am still a bit confused.
Javascript: alert("start"); var so; so = document.embeds[0];
so.addParam("allowScriptAccess","always"); import flash.external.ExternalInterface;
ExternalInterface.call("setValue[2600]");
displays an alert to tell me that it has indeed began to execute
saves the embedded flash file into a variable and sets access
imports that class
calls the method
I am not sure about how this class thing works? This is just the bits and pieces I was able to come up with from that site, but I don't really understand how it all works (but certainly hope to eventually). This is the site: http://bytes.com/topic/flash/answers/694359-how-do-i-access-flash-function-using-javascript. When I execute the code with the importation nothing happens, but the alert does come up when I don't have that statement?
If someone could elaborate on how I might call that method, I would be very thankful! :)
The code you have there is a mix of JavaScript and ActionScript.
In ActionScript, you need to register the setValue function for external use, so it can be called from JavaScript. Code for it could look something like this:
package game
{
import flash.display.Sprite;
import flash.external.ExternalInterface;
import flash.text.TextField;
public class Scores extends Sprite
{
public var txtScore:TextField; // A textfield in the sprite
public function Scores()
{
// Register the function for external use.
ExternalInterface.addCallback("setValue", setValue);
}
private function setValue(value:Number):void
{
txtScore.text = String(value);
}
}
}
And the JavaScript could look something like this:
var so = document.embeds[0];
so.setValue(2600);
Adobe has the documentation with a lengthy but useful example here. They show the ActionScript as well as the JavaScript, and how they can interact in both ways.

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