How To Configure TypeScript and Require in Visual Studio 2017 - visual-studio

Question

Even though this talks about VueJS. I suspect it will work with any other JavaScript language like Angular or React as well.
I have been learning Vue.js and loving it. Knowing I have a larger application on the way and the fact that I have wanted to start using TypeScript. Now seems like the time to do so. I have a firm grasp on Vue at this point but can not find any documentation (over 2 weeks of finding the exact, MINIMUM requirements) on how to setup TS and actually get it to run.
Here is an example of some HTML and Vue code that works with using just script tags and normal JavaScript.
HTML
<div id="app">
<h4>{{ Value }}</h4>
</div>
#section Scripts {
<script src="~/lib/vue/vue.js"></script>
<script src="~/js/test.js"></script>
}
JavaScript - test.js
var app = new Vue({
el: "#app",
data: {
Value: "Hello there"
}
});
This works and produces Hello there on the page.
Configuring TypeScript
This seems straight forward, I have a TypeScripts folder below my js folder where the "source" .ts files will be. The output files will be in the js folder as .js files. Here is my tsconfig.json located in the TypeScripts folder:
{
"compileOnSave": true,
"compilerOptions": {
"noEmitOnError": true,
"noImplicitAny": false,
"outDir": "../",
"removeComments": false,
"sourceMap": true,
"target": "es5",
"module": "amd" // <-- Should this be used?
},
"exclude": [
"node_modules",
"wwwroot"
]
}
This works and I do get .js files each time a save the .ts files.
However, now I want to incorporate Vue into the .ts using it in ways I have seen in videos as well as code online. The following code compiles without errors:
JavaScript - ES6 - test2.ts
const Vue = require("vue")
const app = new Vue({
el: "#app",
data: {
Value: "Hello there"
}
})
Now I update the HTML to the following:
HTML
<div id="app">
<h4>{{ Value }}</h4>
</div>
#section Scripts {
<script src="~/js/test2.js"></script>
}
I reload the page and all I get is the {{ Value }} markup. Plus the JavaScript error: Uncaught ReferenceError: require is not defined.
That seems simple enough, I figure I just add the following line to the Scripts section and remove the single reference to the test2.js file:
#section Scripts {
<script src="~/lib/require.min.js" data-main="/js/test2.js"></script>
}
Reload and now I get: Uncaught Error: Module name "vue" has not been loaded yet for context: _. Use require([]) which references this but that code now seems to diverge from what the .ts file should look like.
The ES6 Test2.ts file seems to be the way people code. The way it wants me to write the require statement in the link above seems far more verbose and does not show up in any code samples I have seen. So I must be missing something. If it helps, the Vue and Require downloads have come from my package.json (npm) file which looks like this:
"devDependencies": {
"#types/node": "^9.4.7",
"requirejs": "^2.3.5",
"vue": "^2.5.16"
...
}
And my bundleconfig.json which puts them in the wwwroot/lib folders where they should go.
{
"outputFileName": "wwwroot/lib/require.min.js",
"inputFiles": ["node_modules/requirejs/require.js"]
},
{
"outputFileName": "wwwroot/lib/vue/vue.js",
"inputFiles": [ "node_modules/vue/dist/vue.js" ]
}
I have to believe I am so close to getting it. Being able to write code in the more modern ES versions is great. I have just not been able to find the right piece of the puzzle to fit it all together.

Answer 1

The main problem above is because in the first "plain JavaScript" example, you are not using modules at all. You are loading the Vue library directly in your page, which creates the global Vue object, and then your script is global (i.e. not a module) and references the Vue object directly.
For the test2.ts file, you mention this is ES6, but you then 'require' in the Vue library. This means the code is now attempting to use modules, but CommonJS modules, not ES6 modules. (Where you would write something like import Vue from "vue"). This means it would require a loader at runtime (e.g. the require.js library you are trying to use), which could work if configured correctly, but generally you'd want something like WebPack to package up Vue.js and your code into a standalone bundle the page loads at runtime.
Note: Edited paragraph below
I've created a sample ASP.NET Core project showing how to configure TypeScript and WebPack to generate a bundle per page using the global Vue.js object via a script tag. I've put an extensive readme on it to explain all the workings. You can see it at https://github.com/billti/SimpleVueApp . If you have further feedback, I'll continue to update it to make it better/clearer.
That said, as you get deep in Vue there is one Visual Studio limitation to be aware of. Currently there is no rich support for .vue files (known in the docs as "single file components"). What I mean by "rich support", is that these files have a certain context that we don't infer right now to provide good IntelliSense (i.e. completion lists, errors, tooltips, etc.). Also, HTML files in Visual Studio (which is what you would open a .vue files as) also only support plain CSS in <style> tags, and plain JavaScript in <script> tags currently, whereas with the right Vue and WebPack setup you can do things like write LESS code directly in your style tags, and write TypeScript directly in your script tags. My team is looking at this currently and hoping to improve this in the near future.
Let me know if any of that isn't clear. Happy to help further.