I'm trying to host a website, and I use a .wasm file with .js scripts created by the wasm-pack tool.
I tested the project locally with npm and node.js and everything worked fine.
But Then I hosted it on a raspberry (apache2), and when I try to access it, I get in the following error:
Failed to load module script: The server responded with a non-JavaScript MIME type of "application/wasm". Strict MIME type checking is enforced for module scripts per HTML spec.
details
There are multiple files, but here is the idea:
my index.html loads the module bootstrap.js
// bootstrap.js content
import("./index.js").catch(e => console.error("Error importing `index.js`:", e));
my main code is in the index.js, which calls test_wasm_bg.js
And finally, test_wasm_bg.js loads the wasm file with this line:
// test_wasm_bg.js first line
import * as wasm from './test_wasm_bg.wasm';
Where is the problem?
What is the right way to load a web assembly file?
I finally found what is the right way to load a wasm application in a wasm-bindgen project!
In fact, everything was on this page
When you compile the project without wanting to run it with a bundler, you have to run wasm-pack build with a --target flag.
wasm-pack build --release --target web.
This creates a .js file (pkg/test_wasm.js in my example) with everything you need to load the wasm-application.
And then this is how you use the functions created by wasm-bindgen (index.js):
import init from './pkg/test_wasm.js';
import {ex_function, ex_Struct ...} from '../pkg/test_wasm.js';
function run {
// use the function ex_function1 here
}
init().then(run)
You include your index.js in your HTML file
<script type="module" src="./index.js"></script>
And then it work's !
Edit:
Now that's I understand the javascript ecosystem a bit more, I cab try to explain what I understand:
There are many ways to do imports in js, here is a list :
https://dev.to/iggredible/what-the-heck-are-cjs-amd-umd-and-esm-ikm
You don't need to know much about that, except that the default target of wasm-pack is a node style ecmascript module. This import will work in node.js, but not directly in the browser. So in node, you can import a function from a wasm file directly, like so:
import {ex_function} from "./test.wasm"
But these styles of import don't work in the browser right now. Maybe it will be possible in the future
But for now, your browser only knows about js modules. So if you try to import a .wasm file directly in the browser, it will throw a mime type error because it doesn't know how to deal with webassembly files.
The tool you use to go from ecmascipt modules (with a lot of nmp packages for example) to a single js file is called a web-bundler (webpack, rollup, snowpack ...). If you work on a big project with npm, you probably need one. Otherwise, the "--target web" will say to wasm-bindgen to instantiate the wasm module the right way (look at the pkg/test_wasm.js)
Related
In my typescript project I need to add the *.js extension when doing imports, otherwise the project will build but it will fail at runtime in the browser because it cannot find the file.
This is what my typescript imports look like:
import {MainApp} from './MainApp.js';
window.onload = () => {
var app = new MainApp(5);
app.doSomething();
};
From what I have read (Appending .js extension on relative import statements during Typescript compilation (ES6 modules) for example) it seems a normal thing for typescript that I cannot do this:
import {MainApp} from './MainApp.js';
But the thing is that in Angular using typescript I can do this:
import {MainApp} from './MainApp';
So, how it is Angular doing it? There is a way I can replicate that behavior in my non angular, pure typescript project?
Because angular cli first compiles all your source files into fewer files for the browser. All your code from multiple files lands in just one .js file. At compile time the compiler finds the MainApp related file and puts it into the output file.
Whereas the typescript compiler for the most part just removes the TS parts and keeps the TS parts. Otherwise it doesn't touch the files. The browser then at runtime requests all the source .js files.
If you don't want to care about file endings in import you'll need a bundler. There are many different ones like webpack, rollup, parcel, and many more.
I am creating an app with Electron and Vue (using js not ts).
When I run the app using npm run electron:serve the app runs fine.
I now want to build a Windows exe so I can distribute my app. I have tried using electron-builder, electron-packager and electron-forge. Whenever I can get the build to finish, running the exe throws the cannot use import statement outside a module error (referring to the first import statement it finds, i.e. import { app, protocol, BrowserWindow } from 'electron').
I've tried adding "type":"module" to my package.json but (due a bug in Vue, according to this question), that throws Error [ERR_UNSUPPORTED_ESM_URL_SCHEME]
I've also tried changing all my import statements to require but this doesn't work because some of the node modules I'm using use import and the error just throws for those instead.
I'm tearing my hair out over this. Where do I go from here?
UPDATE:
I have found a workaround for the Vue bug and posted my findings on the linked question. I can now add "type":"module" to my package.json.
However, I now get an error thrown when I run npm run electron:serve and from my built exe:
Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: <my_project_root>\dist_electron\index.js
require() of ES modules is not supported.
require() of <my_project_root>\dist_electron\index.js from <my_project_root>\node_modules\electron\dist\resources\default_app.asar\main.js is an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which defines all .js files in that package scope as ES modules.
To be clear, I'm not using require in any of my source code, but the compiled(?) version does?
What's going on here?
UPDATE 2:
As requested, here is a minimal reproducible example that maintains original folder structure, configs and package.json
I am trying to call a function in a python file from a js file, I got this to work through my console, but I am now trying to implement it in a mobile app using expo.
The way I had set this up is, I have the JS file for a certain screen in my app, this then calls a function in a separate JS file, which then calls the function in the python file.
I am using the child_process module to talk to python from JS.
And as I said, this was working before I tried to export the JS function to my screen file.
index.js
export function foo(process, sentence){
const spawn = require("child_process").spawn;
const process = spawn("python3", ["./python.py", sentence]);
...
}
screen.js
*other imports
import { foo } from "./filepath..."
...
But when I run npm start I get the following error:
Failed building JavaScript bundle.
While trying to resolve module `child_process` from file `/Users/mee/Documents/GitHub/project/app/screens/screen.js`, the package `/Users/mee/Documents/GitHub/project/node_modules/child_process/package.json` was successfully found. However, this package itself specifies a `main` module field that could not be resolved (`/Users/me/Documents/GitHub/project/node_modules/child_process/app/screens/screen.js`. Indeed, none of these files exist:
How can I fix this?
It won't work for few reasons
child_process is part of the node standard library, it's not available in other environments like react-native or browser
even if above was not true, there is no python3 executable on your phone
python.py file from your local directory wouldn't be even uploaded to the phone because bundler is only uploading one big js file with entire js code combined + assets, python.py is neither of those.
Only solution that make sense it to rewrite that code to javascript.
Technically it's not impossible, there might be a way to do that, by compiling python interpreter for mobile platform, or using some tool that translates python code into js, but it's not something that you should consider.
I have a js file called project specific js.js and in that file I want to import another js file for general js called logic.js in the js folder
import 'js/logic.js';
in devtools when I run the html that imports project specific js i get
Uncaught SyntaxError: Cannot use import statement outside a module
issue fixed it turns out because I wasn't running a localhost for some reason you cant import other js files except modules like react. now I am running localhost and in the script tag importing projectSpecificJs.js i have type set to module so :<script type="module" src="projectSpeceficJs.js></script>"
Just for further information:
import 'file.js'
Is only for nodejs / module html attribute
Also here's some quick info related to the topic:
The whole concept behind using the “import” statement instead of “require” in Node.js is to shift from the CommonJS module system to the ECMAScript Module System. Reference
I'm really new to Typescript2. I'm loving it and have written a module that I can easily import and use in other Typescript2 projects. But I also want my library to be able to be used as a standalone by simply using an HTML tag. When I do that, though, the browser complains "exports is undefined."
I'm guessing I have to write some sort of javascript that imports my module and instantiates it, and then have my browser load that wrapper script. Am I on the right track? How do I create a typescript that transpiles into something that I can just load natively in the browser with a script tag that just loads and instantiates?
You are on the right track. What you need is a module loader. For the browser, requirejs is mentioned in the typescript documentation, although there are several options (requirejs, browserify, webpack, rollup).
I use requirejs with typescript, so I have experience doing the following steps:
For requirejs, you could do the following to get started.
Ensure that you are compiling to modules in the AMD format when running the typescript compiler command (tsc) by using the typescript configuration file or command-line compiler option arguments
// tsconfig.json
{
"compilerOptions": {
"module": "amd"
}
}
Get requirejs
One source is http://requirejs.org/docs/download.html
Note the name of the .js file that is output by the typescript compiler
For example "my-script.js"
Add a script tag to the page
For example <script data-main="scripts/my-script" src="require.js"></script>
There is a simple "getting started" page for requirejs http://requirejs.org/docs/start.html
As a bonus, to export multiple modules to a single file, you can use the --outFile compiler option for typescript.