viewmill
Features | Installation | Getting Started | Notes | Examples
viewmill is aimed to create complex UIs from a simple form of JSX. It statically transforms *.jsx and *.tsx files to reactive views in JavaScript or TypeScript correspondingly, so they could be easily used in Web Components, inserted into DOM or integrated with other libraries and frameworks.
In other words, the tool transpiles JSX to a code in JS, which creates its DOM nodes from generated templates and manipulates them directly, so there's no Virtual DOM.
You can think of the views in terms of MVVM: after being instantiated, they could be inserted into DOM via the insert method (the view) and their state could be modified by updating parameters of the model field (the viewmodel).
Note: a view cannot update its state from the inside.
The tool is written in Rust and based on swc (Speedy Web Compiler) to parse and emit code.
Features
viewmill supports all the valid JSX syntax, including:
- conditionals via the ternary operator:
{loading
? <span>Loading...</span>
: <strong>Loaded!</strong>}
- conditionals via the logical AND (
&&) operator:
{loading && <span>Loading...</span>}
Under the hood viewmill considers it a short form of the ternary operator, when the third operand is null, e.g. a && b is actually a ? b : null.
- loops via the spread child syntax:
<>{...items}</>
<ul>
{...items.map((entry, idx) => (
<li>{idx + 1}: {entry}</li>
))}
</ul>
There're no non-standard HTML attributes or other specific syntax, but it's worth to see the corresponding notes.
Installation
npm i --save-dev viewmill && npm i viewmill-runtime
Getting Started
To demonstrate how the tool works, its basic principles and how to use it, let's create a counter :)
First of all we create a directory for our project and call npm init there:
mkdir counter
cd counter
npm init
Then we install viewmill (as a developer dependency):
npm i --save-dev viewmill
... and its runtime (as a dependency to use in production):
npm i viewmill-runtime
Let's create an src directory and put our counter.tsx there:
// src/counter.tsx
export default (count: number) => {
return <>
<h1>Counter</h1>
<p>The current value is <strong>{count}</strong>!</p>
</>;
}
Then transform it with viewmill by calling:
npx viewmill --suffix "-view" src
It'll create a file src/counter-view.ts:
// src/counter-view.ts
import * as viewmill from "viewmill-runtime";
export default function(count: number) {
return viewmill.view({
count: viewmill.param(count)
}, ({ count }, unmountSignal) => {
return [
viewmill.el("<h1>Counter</h1>"),
viewmill.el("<p>The current value is <strong><!></strong>!</p>", (container, unmountSignal1)=>{
const p__1 = container.firstChild;
const strong__1 = p__1.firstChild.nextSibling;
const anchor__1 = strong__1.firstChild;
viewmill.unmountOn(unmountSignal1, viewmill.insert(viewmill.expr(()=>(count.getValue()), [
count
]), strong__1, anchor__1));
})
];
});
};
Ok, so now we need to bundle our code and finally look at it. One could choose not to bundle and arrange everything manually, but here we're going to use esbuild:
npm i --save-dev esbuild
Then let's create two additional files: src/index.html and src/index.ts.
<!-- src/index.html -->
<html>
<head>
<title>Counter</title>
</head>
<body>
<div id="app"></div>
<script src="../dist/index.js"></script>
</body>
</html>
// src/index.ts
import Counter from "./counter-view";
// you can also use the `new` operator here, e.g. `new Counter(0)`
const view = Counter(0);
view.insert(document.getElementById("app"));
Run the bundler:
npx esbuild src/index.ts --bundle --outdir=dist --target=es6
So finally we can open index.html in a browser and it'll show the counter telling us "The current value is 0!".
Let's modify src/index.ts a bit:
// src/index.ts
import Counter from "./counter-view";
const view = Counter(0);
view.model.count.setValue(1);
view.insert(document.getElementById("app"));
We need to re-run the transformation and bundling commands, and then refresh the opened page. Now it says "The current value is 1!" and that's correct.
Now let's make things more dynamic and add a button to increment the counter:
// src/counter.tsx
export default (count: number) => {
return <>
<h1>Counter</h1>
<p>The current value is <strong>{count}</strong>!</p>
<div>
<button>Increment</button>
</div>
</>;
}
But how to handle the click?
Remember, we cannot mutate parameters from inside the view, so if we write smth like:
<button onclick={() => (count += 1)}>Increment</button>
... it won't work, because the handler will be transformed to () => (count.getValue() += 1), which is invalid and meaningless.
What's the correct way? So viewmill supports two basic patterns for that:
- Provide it as a parameter
- Query necessary node or nodes with a selector
Event Handler via Parameter
// src/counter.tsx
export default (count: number, onClick: (e: Event) => void) => {
return <>
<h1>Counter</h1>
<p>The current value is <strong>{count}</strong>!</p>
<div>
<button onclick={onClick}>Increment</button>
</div>
</>;
}
// src/index.ts
import Counter from "./counter-view";
const view = Counter(0, () => {
view.model.count.updateValue((c) => (c + 1));
});
view.insert(document.getElementById("app"));
Query Selector & Event Listener
// src/counter.tsx
export default (count: number) => {
return <>
<h1>Counter</h1>
<p>The current value is <strong>{count}</strong>!</p>
<div>
<button>Increment</button>
</div>
</>;
}
// src/index.ts
import Counter from "./counter-view";
const view = Counter(0);
const { querySelector } = view.insert(document.getElementById("app"));
querySelector("button")?.addEventListener("click", () => {
view.model.count.updateValue((c) => (c + 1));
});
The querySelector method uses the very standard CSS selectors. There's the querySelectorAll method also.
Removing & Unmounting
If at some point an inserted view should be removed, the insert method returns the necessary functionality:
const {
// Every insertion is associated with a specific `AbortController`,
// which is aborted on `remove` or `unmount`, so this property is
// its `AbortSignal`
unmountSignal,
// Removes the inserted nodes from DOM and triggers the signal
remove,
// Unmounts the inserted nodes without the actual removing and triggers the signal.
// Useful if there's no need to affect DOM.
unmount
} = view.insert(...);
So if we need to remove the counter:
const { unmountSignal, remove } = view.insert(document.getElementById("app"));
unmountSignal.addEventListener("abort", () => console.log("Bye!"));
remove();
Web Components
The viewmill views are intended to be a part of Web Components. So here's an axample of how to create one for the counter:
// src/my-counter.ts
import { InsertedView } from "viewmill-runtime";
import Counter from "./counter-view";
customElements.define("my-counter", class extends HTMLElement {
private view = Counter(0);
private insertedView?: InsertedView;
private get counter() {
return this.view.model.count;
}
connectedCallback() {
if (this.isConnected) {
const inserted = this.view.insert(this);
const {
unmountSignal: signal,
querySelector
} = inserted;
querySelector("button")?.addEventListener("click", () => {
this.counter.updateValue((c) => c + 1);
}, { signal });
// ^^^^^^ Please, note how we use the signal here
this.insertedView = inserted;
}
}
disconnectedCallback() {
// The element and all its children are being removed here,
// so it's ok just to unmount the view to trigger the `unmountSignal`
this.insertedView?.unmount();
this.insertedView = null;
}
static get observedAttributes() {
return ["value"];
}
attributeChangedCallback(name: string, _?: string, newValue?: string) {
if (name === "value") {
this.counter.setValue(+newValue);
}
}
});
Then we can modify the index.ts file:
// src/index.ts
export * from "./my-counter";
... and the index.html file:
<!-- src/index.html -->
<html>
<head>
<title>Counter</title>
</head>
<body>
<script src="../dist/index.js"></script>
<my-counter></my-counter>
<my-counter value="123"></my-counter>
</body>
</html>
Custom Components
Every custom component is just a function with the props argument, which returns an Insertable:
function <Props extends object>(props: Props): Insertable;
Children are available via the children property. The value can be an Insertable, an array of them or undefined.
Let's see how we can extend things with custom components by examples. Please, note how actively the viewmill-runtime library is used.
If
This component helps us to code condtions with JSX.
// src/if.ts
import { Insertable, Insertion, Live, Unmounter, insert } from "viewmill-runtime";
// Show children when the `test` is truthy
export default (
{ test, children }: {
test: unknown | Live<unknown>,
children?: Insertable | Insertable[]
}
): Insertable => {
// `Live` is a non-static value
if (test instanceof Live) {
// This wrapper is for working with DOM
return new Insertion((target, anchor) => {
// An anchor to avoid jumping around when updating, cause
// the content could be re-inserted at the wrong place
const a = target.insertBefore(
document.createComment("if"),
anchor
);
// This controller helps to stop listening to the
// `test` updates on unmount
const abortController = new AbortController();
// This is needed to remove the inserted `children`
let un: Unmounter | null = null;
// Introducing a handler here to not repeat ourselves
const update = () => {
if (test.getValue() && !un) {
un = insert(children, target, a);
} else {
un?.(true);
un = null;
}
};
// Listening to the `test` updates
test.listen(update, abortController.signal);
// Check the `test` value on a first insertion
update();
// The `Insertion` callback needs to return an unmounter
// to clean up its things if necessary
return (removing) => {
abortController.abort();
un?.(removing);
if (removing) {
target.removeChild(a);
}
};
});
} else if (test) {
// The `test` value is static, so let's just
// return `children` if it's truthy
return children;
}
// `Insertable` could be undefined, so no need to return anything here
};
Here's an example how to use it:
import If from "./if";
export default (count: number) => {
return <>
<If test={count > 10}>
The <code>count</code> is {count}, which is
obviously greater then 10!
</If>
<If test={123}>
<p>That's truthy!</p>
</If>
</>;
}
For
Iterating over an array using a function, which is provided as a child.
// src/for.ts
import { Insertable, Insertion, Live, Unmounter, insert } from "viewmill-runtime";
export default <E extends Insertable>(
{ items, using }: {
items: E[] | Live<E[]>,
using: (item: E, index: number) => Insertable
}
): Insertable => {
if (items instanceof Live) {
return new Insertion((target, anchor) => {
// The content is being removed on every update here too,
// so we need this anchor to stabilize the placement
const a = target.insertBefore(
document.createComment("for"),
anchor
);
let unmounters: (Unmounter | null)[] = [];
const unmount = (removing: boolean) => {
unmounters.forEach((u) => u?.(removing));
unmounters = [];
};
const update = () => {
// Remove the previously inserted items if any
unmount(true);
// Insert the new ones
unmounters = items.getValue()
.map(using)
.map((entry) => insert(entry, target, a));
};
const abortController = new AbortController();
items.listen(update, abortController.signal);
update();
return (removing) => {
abortController.abort();
unmount(removing);
if (removing) {
target.removeChild(a);
}
};
});
} else {
// Just a static iterable
return items.map(using);
}
};
Both static and non-static usages:
import For from "./for";
export default (items: string[]) => {
return <>
<ul>
<For
items={items}
using={(s, idx) => <li>#{idx}: {s}</li>}
/>
</ul>
<For
items={[1, 2, 3]}
using={(n) => <><br />number: {n}</>}
/>
</>;
}
Extendable List & userData
It's possible to enrich a component behaviour, using userData while listening to a live param.
For instance let's create an extendable list, so it's possible to add items there without its full re-rendering:
// src/xlist.ts
import { Insertable, Insertion, Live, Unmounter, insert } from "viewmill-runtime";
export default function <E extends Insertable>(
{ items, using }: {
items: E[] | Live<E[]>,
using: (item: E, index: number) => Insertable
}
): Insertable {
if (items instanceof Live) {
return new Insertion((target, anchor) => {
// Let's use a container here to show how to unmount
// its children
const container = document.createElement("div");
let unmounters: (Unmounter | null)[] = [];
const unmount = (removing: boolean) => {
unmounters.forEach((u) => u?.(removing));
unmounters = [];
};
const insertItems = (items: E[]): (Unmounter | null)[] => (
items
.map(using)
.map((entry) => insert(entry, container))
);
const update = (tail?: unknown) => {
if (typeof tail === "number" && tail > 0) {
// Just insert the new items
unmounters.push(
...insertItems(items.getValue().slice(-tail))
);
} else {
// The defalt behaviour is to replace everything
unmount(true);
unmounters = insertItems(items.getValue());
}
};
const abortController = new AbortController();
// Handling `userData` on every change
items.listen(({ userData }) => update(userData), abortController.signal);
update();
// Don't forget to insert the container
target.insertBefore(container, anchor);
return (removing) => {
abortController.abort();
// No need to remove the inserted items no matter what
// the `removing` argument is, cause they're all children
// of the container, ...
unmount(false);
if (removing) {
// ... which is being removed here
target.removeChild(container);
}
};
});
} else {
return items.map(using);
}
};
Numeric list view:
// src/xnumlist.tsx
import ExList from "./xlist";
export default (items: number[], onClick: () => void) => (
<>
<ExList
items={items}
using={(n) => <><br />{n}</>}
/>
<p>
<button onclick={onClick}>Load next</button>
</p>
</>
);
The button adds new 3 items to the list on every click:
// src/index.ts
import ExNumList from "./xnumlist-view";
const xlist = ExNumList([1, 2, 3, 4], () => {
const { items } = xlist.model;
const n = 3;
items.updateValue(
(current) => {
const lastItem = current[current.length - 1];
// Generate next items
const next = Array.from({ length: n }, (_, k) => lastItem + k + 1);
return current.concat(next);
},
// Here goes the `userData` value, so the view'll insert
// only the last `n` items of the updated value
n
)
});
xlist.insert(document.getElementById("app"));
Fetching Data
A very simple component to fetch remote data:
// src/fetcher.ts
import { Insertable, Insertion } from "viewmill-runtime";
export default function ({ url }: { url: string }): Insertable {
return new Insertion((target, anchor) => {
const abortController = new AbortController();
const info = document.createElement("div");
info.textContent = "Loading...";
fetch(url, { signal: abortController.signal })
// ^^^^^^ Stop fetching if aborted
.then(() => info.textContent = "Loaded!")
.catch((e) => info.textContent = `[ERROR] ${e}`);
target.insertBefore(info, anchor);
return (removing) => {
// Aborting the controller on unmount
abortController.abort();
if (removing) {
target.removeChild(info);
}
};
});
}
Fetching one remote url and a local one:
// src/fetching.tsx
import Fetcher from "./fetcher";
export default () => (
<>
<Fetcher url="https://github.com" />
<Fetcher url="/" />
</>
);
// src/index.ts
import Fetching from "./fetching-view";
const view = Fetching();
view.insert(document.getElementById("app"));
Notes
Typescript Configuration
{
"compilerOptions": {
"jsx": "preserve",
"jsxImportSource": "viewmill-runtime"
}
}
The jsxImportSource option here fixes the JSX element implicitly has type 'any' because no interface 'JSX.IntrinsicElements' exists. ts(7026) error if noImplicitAny or strict enabled.
HTML
Boolean Attribute
Let's consider a simple example:
export default (flag: boolean) => (
<input type="checkbox" checked={flag} />
);
As a result, the checked attribute is present if the flag value is true, and is absent otherwise.
It also works for the spread attributes syntax:
export default (flag: boolean) => (
<input type="checkbox" {...{ checked: flag }} />
);
Please, note if a value is null or undefined it's necessary to convert it explicitly:
export default (flag?: boolean | null) => (
<input type="checkbox" checked={!!flag} />
);
Remove Attribute
Just set its value to false as it's shown in the section above.
Toggle Attribute
There's no specific syntax for that, but you can introduce a custom function:
export function cls(v: Record<string, boolean | undefined | null>): string | false {
const c = Object.keys(v).filter((k) => !!v[k]);
return c.length > 0 ? c.join(" ") : false;
}
So it can be used like:
import { cls } from "./utils";
export default (a?: boolean | null) => (
<div class={cls({ enabled: a, disabled: !a })}>
<code>{a}</code>
</div>
);
Examples
Table
A table with sorting and paging.
- The whole view is defined in just one file (see
src/table.tsx) - Written in Typescript
- Data from Random User Generator
- CSS by Bootstrap
- Bundled and served with esbuild
Form
A form with dynamic fields and validation.
- The whole view is defined in just one file (see
src/form.tsx) - Written in Typescript
- CSS by Bootstrap
- Bundled and served with esbuild
2 Jan 21, 2022
1 Apr 21, 2022
10 Sep 4, 2023
11 Dec 30, 2022
16 Dec 12, 2022
4 Jun 6, 2023
4 Oct 21, 2023
1 Jan 1, 2022
22 Apr 4, 2023
2 Nov 27, 2022
2 Nov 27, 2022
50 Jan 29, 2023
5 Jan 22, 2023
36 Jan 28, 2023
5 Jan 16, 2023
11 Jan 25, 2023
4 Feb 26, 2023
35 Apr 8, 2023
13 May 4, 2023