I am currently using the following package where the readme illustrates the following
final bool loaded = await JsIsolatedWorker().importScripts(['test.js']);
I am using the isolate worker package so my code can work on web and outside of web. I would like to generate javascript code from my dart code. I have one file with a top level function and I use
dart compile js -O0 -o test.js test.dart
which I found here
https://dart.dev/tools/dart2js
this is my dart file
void main(List<String> args) {
doComputation('');
}
String doComputation(String input) {
return 'output';
}
I can generate javascript only if I have a main function but this generates a javascript file where the doComutation is not a top level function, so I am not sure if the package can call the function. It looks like it generates an entire program instead of just generating one function.
The generated file is too long to post
So what my question comes down to is this. Is there a way to generate javascript from dart for 1 function with its dependencies included instead of having to generate the entire program? So that I can call this function from dart.
I am not an expert but I also had this problem. Here's what worked for me:
In web_worker.dart:
import 'package:js/js.dart';
main(){
allowInterop(doComputation);
}
#JS('doComputation')
String doComputation(String computationInput) {
// Replace this with your actual computation.
final String computationOutput = "output";
return computationOutput;
}
Compile it using:
$ dart compile js web_worker.dart -o webWorker.js
Manually edit webWorker.js, the JS file generated by the compiler:
Delete this line at the top of the file:
(function dartProgram() {
and the line at the bottom of the file with the corresponding closing brace:
})();
I don't understand what's going on here but I found the Javascript version of the function doComputation() defined in webWorker.js as a property of the object "A".
I defined a wrapper at the top of the file like this:
function doComputation(computationInput) {
return A.doComputation(computationInput)
}
and then I was able to use the file with JsIsolatedWorker like this:
final bool loaded =
await JsIsolatedWorker().importScripts(['../web/webWorker.js']);
if (loaded) {
final String computationResult = await JsIsolatedWorker()
.run(functionName: 'doComputation', arguments: computationInput);
} else {
debugPrint('Web worker is not available');
}
If someone who understands this better can elaborate or improve on this solution, that would be great. I don't really have any idea what I'm doing. I'm just posting this to hopefully help other people save time in the future by sharing what worked for me.
You can use js package to call JavaScript APIs from Dart code, or vice versa. To make a Dart function callable from JavaScript by name, use a setter annotated with #JS().
#JS()
library callable_function;
import 'package:js/js.dart';
/// Allows assigning a function to be callable from `window.functionName()`
#JS('functionName')
external set _functionName(void Function() f);
/// Allows calling the assigned function from Dart as well.
#JS()
external void functionName();
void _someDartFunction() {
print('Hello from Dart!');
}
void main() {
_functionName = allowInterop(_someDartFunction);
}
JavaScript code may now call functionName() or window.functionName().
Check google chartjs https://github.com/google/chartjs.dart/tree/master/example for a complete example.
From dart2js "Helping dart2js generate better code" there is a tip :
Don’t worry about the size of your app’s included libraries. The dart2js compiler performs tree shaking to omit unused classes, functions, methods, and so on. Just import the libraries you need, and let dart2js get rid of what you don’t need.
Related to this post https://stackoverflow.com/a/21124252/3733730.
You can do this instead by using the package dart2js
one make a program for your main.dart dart2js where the function or command you wanted to make is there, then create a separate dart file what function you wanted to call, and it will fix your problem, it is a separate file but will only execute one function that you needed to do so and that is the separate file
Related
I am attempting to embed v8 into my application, I am messing about seeing what is included in the V8 environment (duktape does not include a console implementation) and it seems like v8 does include an implementation however when I call console.log it does not print anything, instead it just prints undefined (which i assume to be the return value of console.log) So how would one go about linking the default std::cout output with console.log.
This is my code currently, I am working with the default hello world code very slightly modified.
int main(int argc, char* argv[]) {
// Initialize V8.
v8::V8::InitializeICUDefaultLocation(argv[0]);
v8::V8::InitializeExternalStartupData(argv[0]);
std::unique_ptr<v8::Platform> platform = v8::platform::NewDefaultPlatform();
v8::V8::InitializePlatform(platform.get());
v8::V8::Initialize();
// Create a new Isolate and make it the current one.
v8::Isolate::CreateParams create_params;
create_params.array_buffer_allocator =
v8::ArrayBuffer::Allocator::NewDefaultAllocator();
v8::Isolate* isolate = v8::Isolate::New(create_params);
{
v8::Isolate::Scope isolate_scope(isolate);
// Create a stack-allocated handle scope.
v8::HandleScope handle_scope(isolate);
// Create a new context.
v8::Local<v8::Context> context = v8::Context::New(isolate);
// Enter the context for compiling and running the hello world script.
v8::Context::Scope context_scope(context);
{
// Create a string containing the JavaScript source code.
v8::Local<v8::String> source =
v8::String::NewFromUtf8(isolate, R"(
console.log("does not print?")
)",
v8::NewStringType::kNormal)
.ToLocalChecked();
// Compile the source code.
v8::Local<v8::Script> script =
v8::Script::Compile(context, source).ToLocalChecked();
// Run the script to get the result.
v8::Local<v8::Value> result = script->Run(context).ToLocalChecked();
// Convert the result to an UTF8 string and print it.
v8::String::Utf8Value utf8(isolate, result);
printf("%s\n", *utf8);
}
}
// Dispose the isolate and tear down V8.
isolate->Dispose();
v8::V8::Dispose();
v8::V8::ShutdownPlatform();
delete create_params.array_buffer_allocator;
std::cin.get();
return 0;
}
and I am using the prebuilt v8 binaries here
Try the following:
#include "src/debug/interface-types.h"
define your own "console delegate" class, deriving from debug::ConsoleDelegate
override any methods you're interested in, e.g. void Log(const debug::ConsoleCallArguments& args, const v8::debug::ConsoleContext&) override;
instantiate it and call debug::SetConsoleDelegate(isolate, &your_console_delegate); after creating your Isolate
To see an example, start at https://cs.chromium.org/chromium/src/v8/src/d8/d8-console.h?l=14&gsn=D8Console and trace where it's used.
So for anyone in the future that is dealing with this, this is the process I used to fix it.
download the source from here, only the src folder is needed.
extract it and link it in to your project where ever you put vendor code in addition to the bundle.
put it in the a src folder because otherwise its includes don't work
you will need to make a bunch of include directories for it to compile, mine include v8/src, and v8
make sure to link it with the nuget package, you may not have to do this, one machine needed it the other didn't.
you do not need to generate builtins-generated/bytecodes-builtins-list.h
I have a large (~15k LoC) JS app (namely a NetSuite app) written in old-style all-global way. App consists of 26 files and dependencies between them are totally unclear.
The goal is to gracefully refactor the app to smaller modules. By gracefully I mean not breaking\locking the app for long time, but doing refactoring in smaller chunks, while after completing each chunk app remains usable.
An idea I have here is to concat all the JS files we have now into single-file bundle. After that some code could be extracted into modules. And the legacy code could start importing it. The modules & imports should be transpiled with webpack\whatever, while legacy code remains all-globals style. Finally all this is packed into single JS file and deployed.
My questions are
is there a better approach maybe? This sounds like a typical problem
are there any tools available to support my approach?
I gave webpack a try and I haven't managed to get what I want out of it. The export-loader and resolve-loader are no options because of amount of methods\vars that needs to be imported\exported.
Examples
Now code looks like
function someGlobalFunction() {
...
}
var myVar = 'something';
// and other 15k lines in 26 files like this
What I would ideally like to achieve is
function define(...) { /* function to define a module */ }
function require(moduleName) { /* function to import a module */ }
// block with my refactored out module definitions
define('module1', function () {
// extracted modularised code goes here
});
define('module2', function () {
// extracted modularised code goes here
});
// further down goes legacy code, which can import new modules
var myModule = require('myNewModule');
function myGlobalLegacyFunction() {
// use myModule
}
I'm following an approach similar to that outlined here: https://zirho.github.io/2016/08/13/webpack-to-legacy/
In brief:
Assuming that you can configure webpack to turn something like
export function myFunction(){...}
into a file bundle.js that a browser understands. In webpack's entry point, you can import everything from your module, and assign it to the window object:
// using namespace import to get all exported things from the file
import * as Utils from './utils'
// injecting every function exported from utils.js into global scope(window)
Object.assign(window, Utils).
Then, in your html, make sure to include the webpack output before the existing code:
<script type="text/javascript" src="bundle.js"></script>
<script type="text/javascript" src="legacy.js"></script>
Your IDE should be able to help identify clients of a method as you bring them into a module. As you move a function from legacy.js to myNiceModule.js, check to see if it still has clients that are aware of it globally - if it doesn't, then it doesn't need to be globally available.
No good answer here so far, and it would be great if the person asking the question would come back. I will pose a challenging answer saying that it cannot be done.
All module techniques end up breaking the sequential nature of execution of scripts in the document header.
All dynamically added scripts are loaded in parallel and they do not wait for one another. Since you can be certain that almost all such horrible legacy javascript code is dependent on the sequential execution, where the second script can depend on the first previous one, as soon as you load those dynamically, it can break.
If you use some module approach (either ES7 2018 modules or require.js or you own) you need to execute the code that depends on the loading having occurred in a call-back or Promise/then function block. This destroys the implicit global context, so all these spaghetti coils of global functions and var's we find in legacy javascript code files will not be defined in the global scope any more.
I have determined that only two tricks could allow a smooth transition:
Either some way to pause continuation of a script block until the import Promise is resolved.
const promise = require("dep1.js", "dep2.js", "dep3.js");
await promise;
// legacy stuff follows
or some way to revert the scope of a block inside a function explicitly into the global scope.
with(window) {
function foo() { return 123; }
var bar = 543;
}
But neither wish was granted by the javascript fairy.
In fact, I read that even the await keyword essentially just packs the rest of the statements into function to call when promise is resolved:
async function() {
... aaa makes promise ...
await promise;
... bbb ...
}
is just, I suppose, no different from
async function() {
... aaa makes promise ...
promise.then(r => {
... bbb ...
});
}
So this means, the only way to fix this is by putting legacy javascript statically in the head/script elements, and slowly moving things into modules, but continue to load them statically.
I am tinkering with my own module style:
(function(scope = {}) {
var v1 = ...;
function fn1() { ... }
var v2 = ...;
function fn2() { ... }
return ['v1', 'fn1', 'v2', 'fn2']
.reduce((r, n) => {
r[n] = eval(n);
return r;
}, scope);
})(window)
by calling this "module" function with the window object, the exported items would be put on there just as legacy code would do.
I gleaned a lot of this by using knockout.js and working with the source readable file that has everything together but in such module function calls, ultimately all features are on the "ko" object.
I hate using frameworks and "compilation" so generating the sequence of HTML tags to load them in the correct order by the topologically sorted dependency tree, while I could write myself such a thing quickly, I won't do this, because I do not want to have any "compilation" step, not even my own.
UPDATE: https://stackoverflow.com/a/33670019/7666635 gives the idea that we can just Object.assign(window, module) which is somewhat similar to my trick passing the window object into the "module" function.
I was playing with WebAssembly and so far and I was able to manage emscripten compile my test C++ project to wasm file
em++ provides me 2 files i.e.
mainTest.js mainTest.wasm
When I load mainTest.js in my html page then I get a JavaScript object called
"Module".
I did found how to call C++/wasm methods from javascript i.e. something like:
var myTestInteger = Module._callMyTestMethod();
and read strings from the
Module.wasmMemory.buffer
, but I do NOT understand how to call JavaScript from C++ code.
i.e. I would like to be able to do something like that:
#ifdef __cplusplus
extern "C" {
#endif
extern void testExternJSMethod();
int main()
{
cout << " Hello From my Test1 !" << endl;
testExternJSMethod();
return 0;
}
int EMSCRIPTEN_KEEPALIVE callMyTestMethod(){
return 26;
}
#ifdef __cplusplus
}
#endif
and the my js method testExternMethod that I am loading in another js file called utils.js
function testExternMethod() {
console.log("Hello from testExternMethod!" + )
}
Here I would like to call the JavaScript testExternJSMethod from C++.
When I run the page in Firefox get "-1" in the debugger console.
So what I am missing in this case? Unfortunately The Mozilla documentation is giving only examples in those S-expressions instead of C++.
What am I missing in example? In C++ I have defined the method with the extern keyword i.e.
extern void testExternJSMethod();
but I get the feeling that that is not all I have to do.
I believe that I should somehow link that JavaScript method to the Module somehow but I do not know how.
Module.asm gives me the exports. Which method call should give me the imports? since I believe that this _testExternJSMethod() should be in some imports method I can not figure out how to get to it.
I'm not exactly sure of your use case, but you are missing important steps to be able to use your function testExternalJSMethod. You have two options here:
Option 1 - Library
1 - Define your function in c/c++ .
extern void testExternalJSMethod();
2 - Create a file called myLibrary.js
3 - The JS function needs to be added to the LibraryManager in your library file with the following code:
function makeAlert(text) {
alert(text);
}
if (typeof mergeInto !== 'undefined') mergeInto(LibraryManager.library, {
testExternalJSMethod: function() {
makeAlert("Hello world");
}
});
4 - If testExternalJSMethod depends on anything outside of its own scope (for example, makeAlert above), make sure to include the script in your html page
<script async type="text/javascript" src="myLibrary.js"></script>
5 - Add option --js-library to your emcc command, and immediately after the relative path to myLibrary.js
emcc ... --js-library myLibrary.js
Option 2 - Passing Pointers
1 - Define your javascript function type in c/c++
typedef void testExternalJSMethod()
2 - Wherever you want this function to be used, accept an int param which will be the function pointer, and cast the pointer to your function
void passFnPointer(int ptr) {
((testExternalJSMethod*)ptr)();
}
3 - Use emscripten's addFunction() and store its returned value (the pointer in c/c++)
var fnPtr = Module.addFunction(function () {
alert("You called testExternalJSMethod");
});
4 - Use the stored pointer value from step 3 to pass to our function passFnPointer
var passFnPointer = Module.cwrap('passFnPointer', 'undefined', ['number']);
passFnPointer(fnPtr);
5 - Add option -s RESERVED_FUNCTION_POINTERS to your emcc command
emcc ... -s RESERVED_FUNCTION_POINTERS=10
Have you tried looking at the Emscripten documentation? It has a whole section on interacting with code that details how to expose C / C++ functions to JavaScript and call JavaScript functions from C / C++.
Emscripten provides two main approaches for calling JavaScript from C/C++: running the script using emscripten_run_script() or writing “inline JavaScript”.
It is worth noting that the Mozilla documentation details plain WebAssembly, whereas Emscripten adds a lot more framework and tooling around WebAssembly in order to make it easier to port large C / C++ codebases.
So I've been looking and I found some other questions in stackoverflow but they weren't explained and I didn't understand much. I'm trying to execute functions from a .js file. One of the functions is:
function getRSAKey(mod, exp, pass) {
pubKey = RSA.getPublicKey(mod,exp);
encrypted = RSA.encrypt(pass, pubKey);
return encrypted;
}
As you see this function calls other functions, this is quite a big file and there's no way I can "translate" it to Java, so I have to call the .js file within it. So far I think I need to create an String with the .js file, so that's what I have in my .java file:
BufferedReader script = new BufferedReader(new FileReader("rsa.js"));
Context context = Context.enter();
ScriptableObject scope = context.initStandardObjects();
How can I do to call the function getRSAKey with some given paramaters? Also I should handle the return in the .java file!
Thanks
Edit: I forgot to say that the script uses http://silentmatt.com/biginteger/ the class provided in the link. I was able to execute a script, but it says that 'ReferenceError: "BigInteger" is not defined.'
I am trying to build a nice windows phone application with an HTML front end. I want to use TYPESCRIPT to do my processing onto my html page. There is one javascript function which is crucial for my application to work - window.external.notify
This method isn't created till runtime I assume, so I build a javascript wrapper function to determine if it exists when it is called.
if (window.external.notify != undefined)
window.external.notify(msg);
The issue is I need to get my Typescript files to see this function.
I am using Visual Studio 2012 and I have seen the post - How to use an exported function within the local module
The issue is when I just include my javascript file with the function I want to use I get the error TS2095.
error TS2095: Build: Could not find symbol
Any ideas or help or possible SDKs to circumvent this issue?
//notif.js
let notify = function(message) {
alert(message);
}
//test.ts
declare function notify(message: string): any;
if(notify != undefined)
notify("your message");
Make sure notif.js is loaded first.
You need to tell typescript that this function exists on window.external in order to use it. So :
interface External{
notify: Function;
}
if (window.external.notify != undefined)
window.external.notify("your message");