Better-TypeScript

This repository contains various TypeScript type definitions to make working with TypeScript more convenient.

This project goes along with TypeScript types for new JavaScript, which contains TypeScript type definitions for new JavaScript stuff that isn't in TypeScript's standard type definitions. Better-TypeScript depends on TypeScript types for new JavaScript, so it is automatically included if you use Better-TypeScript.

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NPM: better-typescript

GitHub: BenjaminAster/Better-TypeScript

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Install using npm:

npm i --save better-typescript@latest

Reference the type definitions directly in your TypeScript/JavaScript files...

/// <reference types="better-typescript" />

...or include them in your tsconfig.json or jsconfig.json:

{
	"compilerOptions": {
		"types": ["better-typescript"],
	},
}

For worklets, use better-typescript/worklet/<WORKLET_NAME> as the path:

• better-typescript/worklet/audio for audio worklets
• better-typescript/worklet/paint for paint worklets
• better-typescript/worklet/layout for layout worklets
• better-typescript/worklet/animation for animation worklets

/// <reference types="better-typescript/worklet/audio" />

/// <reference types="better-typescript/worklet/paint" />

/// <reference types="better-typescript/worklet/layout" />

/// <reference types="better-typescript/worklet/animation" />

Stuff in this repository

.querySelector() element parser (view source)

A querySelector parser that parses the CSS selector and automatically returns the interface for the respective element:

document.querySelector("a#foo.bar") // HTMLAnchorElement
document.querySelector("form.info input[type=radio][name=test]:nth-of-type(even)") // HTMLInputElement
document.querySelector(".math-output mrow ~ munderover[displaystyle=false]") // MathMLElement
document.querySelector("svg#logo > filter:first-of-type feTurbulence:not([type=fractalNoise])") // SVGFETurbulenceElement
element.querySelectorAll(":scope > li:nth-of-type(odd)") // NodeListOf<HTMLLIElement>

If the element type itself cannot be determined, but the element is a descendant of any SVG or MathML element, the element automacially becomes an SVGElement or MathMLElement, respectively:

document.querySelector("math.formula .fraction") // MathMLElement
document.querySelector("filter#displacement-filter > .noise") // SVGElement
document.querySelector("body > #logo-svg foreignObject[height] msubsup .power") // MathMLElement

Just to be clear: This parser is not written in TypeScript, it's written solely in TypeScript type definitions (files ending in .d.ts). This works similarly to HypeScript.

.matches() (view source)

You can now use element.matches(selector) and Better-TypeScript will automatically detect the element and provide you with its type definitions when using it in an if-statement.

const element = document.querySelector(".foo");

if (element.matches("img")) {
	// `element` has type `HTMLImageElement` in this scope
	element.src = "https://bigrat.monster/media/bigrat.png";
} else if (element.matches("dialog[open]")) {
	// `element` has type `HTMLDialogElement` in this scope
	element.showModal();
} else if (element.matches("body > a#main-link[href]")) {
	// `element` has type `HTMLAnchorElement` in this scope
	element.href = "https://youtube.be/dQw4w9WgXcQ";
} else if (element.matches<HTMLTextAreaElement>(".inputfield")) {
	// `element` has type `HTMLTextAreaElement` in this scope
	element.value = "Hello world!";
}

Service workers (view source)

Working with service workers with type checking enabled is an awful experience by default as in TypeScript, there is no ServiceWorker lib, only a WebWorker one. Stuff like self.registration, self.clients or the fetch event aren't available by default because from TypeScript's perspecitve, self alywas has the type WorkerGlobalScope in workers, not ServiceWorkerGlobalScope. The way you could previously get around this is by declaring a variable const _self = self as unknown as ServiceWorkerGlobalScope; and then working with this _self instead of self as the global object. This is very ugly and hacky, so Better-TypeScript simply provides all service worker related stuff out of the box to all files.

self.addEventListener("fetch", (event) => {
	// `event` has type `FetchEvent`
})

Shared workers (view source)

The same as for service workers also applies to shared workers. You can now use all shared worker related things out of the box.

self.addEventListener("connect", (event) => {
	// `event` has type `MessageEvent`
})

Tuple (view source)

This adds the Tuple type to create fixed length arrays:

// 💩 previos method:
const color: [number, number, number, number] = [255, 0, 0, 255];

// 😎 with Better-TypeScript:
const color: Tuple<number, 4> = [255, 0, 0, 255];

Accept more things (view source)

Many JavaScript functions also accept numbers which then get automatically converted into a string. TypeScript often just accepts strings, so Better-TypeScript adds the ability to call a function with numbers instead of strings.

window.addEventListener("pointermove", (event) => {
	document.documentElement.style.setProperty("--mouse-x", event.clientX); // would be an error without Better-TypeScript
	document.documentElement.style.setProperty("--mouse-y", event.clientY);
});

const searchParams = new URLSearchParams(location.search);
searchParams.set("count", ++count); // would be an error without Better-TypeScript
history.replaceState(null, "", "?" + searchParams.toString());

Also, for some reason, TypeScript doesn't allow calling history.pushState() and history.replaceState() without the unused second parameter. Better-TypeScript adds support for that:

history.replaceState({ someState: 4 });
history.pushState({ someOtherState: 42 });

.cloneNode() (view source)

When calling .cloneNode() on any element or fragment, TypeScript just returns the Node type by default which is not very useful. With Better-TypeScript, .cloneNode() returns the type of the element that it is called on.

const anchorTemplate = document.createElement("a");
anchorTemplate.href = "https://example.com";
anchorTemplate.textContent = "example";
const anchorClone = anchorTemplate.cloneNode(true); // has the type `HTMLAnchorElement` instead of just `Node`

const fragment = document.querySelector("template#foo-template").content;

for (let i = 0; i < 10; i++) {
	const clone = fragment.cloneNode(true); // has the type `DocumentFragment` instead of just `Node`
	clone.querySelector("a.destination").href = "https://example.com";
	document.body.append(clone);
}

Typed OffscreenCanvas options (view source)

When getting a specific canvas context (e.g. "2d", "webgl2", ...) from a normal canvas element, TypeScript automatically detects the context type and gives the the second options parameter the right options type.

const canvas = document.querySelector("canvas");
canvas.getContext("2d", { alpha: false }); // options parameter has type `CanvasRenderingContext2DSettings`

However, when using an OffscreenCanvas, TypeScript does not provide you with these type definitions and gives the options parameter a type of any which is not very useful. Better-TypeScript adds the right options interfaces.

const canvas = new OffscreenCanvas(width, height);
canvas.getContext("2d", { alpha: false }); // the options parameter now has type `OffscreenCanvasRenderingContext2DSettings`

Non-standard stuff (view source)

This includes various non-standard features that are not part of any specification, e.g. Brave's navigator.brave.isBrave(), Firefox' CSSMozDocumentRule or Chromium & WebKit's scrollIntoViewIfNeeded() function. This can also be used for spoofing-resistant browser detection.

const isBrave = await navigator.brave?.isBrave?.();

if (Element.prototype.scrollIntoViewIfNeeded) element.scrollIntoViewIfNeeded(true);
else element.scrollIntoView({ block: "center" });

const isChromium = Boolean(window.chrome || Intl.v8BreakIterator);

TypedArray

This simply provides the TypedArray type as a union type alias of all typed arrays (Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, BigInt64Array, BigUint64Array, Float32Array and Float64Array).

const sendArrayToWASM = (array: TypedArray) => {
	const buffer = array.buffer;
	// do some magic...
	return pointer;
}

Element extensions (view source)

When an element just has a type of Element and not HTMLElement/SVGElement/MathMLElement, properties such as .dataset or .style are not available. Better-TypeScript adds them.

for (const child of document.body.children) {
	child.dataset.foo = "bar"; // error without Better-TypeScript because `child` has type `Element`
}

TreeWalker filters (view source)

When using a SHOW_ELEMENT, SHOW_TEXT or SHOW_COMMENT filter when creating a tree walker, the tree walker just walks over elements, text nodes and comments, respectively. Better-TypeScript provides intelligent typings for these.

const walker = document.createTreeWalker(document.body, NodeFilter.SHOW_TEXT);
while (walker.nextNode()) {
	const currentNode = walker.currentNode; // has type `Text`
}

Callable WebAssembly export functions (view source)

A WebAssembly export can either be a function, a WebAssembly.Global, a WebAssembly.Memory or a WebAssembly.Table. Because TypeScript doesn't know which export has which type, you ironically cannot do anything on an export, not even call it as a function. With Better-TypeScript, an export is function, a WebAssembly.Global, a WebAssembly.Memory and a WebAssembly.Table all at the same time, which allows you to finally call function exports.

const { module, instance } = await WebAssembly.instantiateStreaming(await window.fetch("./test.wasm"));
const result = instance.exports.add(34, 35); // error without Better-TypeScript

DOMParser returns right document type (view source)

Calling DOMParser.prototype.parseFromString() returns the generic Document interface in pure TypeScript. With Better-TypeScript, it returns Document for "text/html" and XMLDocument for "application/xhtml+xml", "application/xml", "image/svg+xml" and "text/xml".

const doc = new DOMParser().parseFromString(svg, "image/svg+xml"); // has type `XMLDocument`

Bubbling ShadowRoot events (view source)

Events of DOM elements inside a ShadowRoot bubble and can be listened for by a ShadowRoot. Better-TypeScript adds support for these events.

customElements.define("my-element", class extends HTMLElement {
	constructor() {
		super();
		this.attachShadow({ mode: "open" });
		this.shadowRoot.append(template.content.cloneNode(true));

		this.shadowRoot.addEventListener("pointerdown", (event) => {
			console.log(event.pointerType); // `event` has type `PointerEvent`
		});
	}
});

Performance entry types (view source)

When calling navigator.performance.getEntriesByType, Better-TypeScript automatically returns an array of the corresponding performance entry type instead of just the generic PerformanceEntry.

const siteLoadingType = performance.getEntriesByType("navigation")[0]?.type; // error without Bettery-TypeScript

DevTools Custom Object Formatters (view source)

Chromium & Firefox DevTools support a feature called Custom Object Formatters that let you customize the appearance and interactivity of objects printed in the JavaScript console (To enable this feature, click Enable custom formatters in the DevTools settings of Chromium or Firefox). Better-TypeScript adds type definitions for this feature.

const recursion = {};
const style = "border: 1px solid red; inline-size: fit-content";
window.devtoolsFormatters = [{
	header: (object) => object === recursion ? ["span", { style }, "Hello"] : null,
	hasBody: (object) => object === recursion,
	body: (object) => ["ol", {}, ["li", {}, "world!"], ["li", {}, ["object", { object }]]],
}];
console.log(recursion);

Event target for HTMLFieldSetElement (view source)

Event.prototype.target is always just EventTarget by default, which is not very helpful. Better-TypeScript adds support for Event.prototype.target and Event.prototype.currentTarget for HTMLInputElement, HTMLSelectElement, HTMLSelectMenuElement and HTMLTextAreaElement (always the element itself) as well as HTMLFieldSetElement (a union type of HTMLInputElement, HTMLSelectElement, HTMLSelectMenuElement and HTMLTextAreaElement). This allows you to group multiple form elements (such as <input type="radio" />) in one <fieldset> and listen to a change with only a single event listener.

<fieldset id="favorite-animal">
	<legend>Choose your favorite animal</legend>
	<label>
		<input type="radio" name="favorite-animal" value="cat" />
		Cat
	</label>
	<label>
		<input type="radio" name="favorite-animal" value="dog" />
		Dog
	</label>
	<label>
		<input type="radio" name="favorite-animal" value="psychrolutes-marcidus" checked />
		Psychrolutes marcidus
	</label>
</fieldset>

let favoriteAnimal: string;
document.querySelector("fieldset#favorite-animal").addEventListener("change", ({ target }) => {
	favoriteAnimal = target.value;
});

InputEvent interface for "input" event types (view source)

When the browser fires an "input" event, the event usually is an InputEvent. But because there are situations where it just has the generic Event type (e.g. with an <input type="range" />), TypeScript always gives "input" events the Event interface as its type, which makes working with it very impractical. Better-TypeScript reverts this and makes "input" events always have the InputEvent type so that you can use its properties (specifically data, dataTransfer, inputType, isComposing and getTargetRanges()).

element.addEventListener("input", (event) => {
	// `event` now has type `InputEvent`
	console.log(event.inputType);
});

execCommand command id enum (view source)

Better-TypeScript adds enum values for the commandId parameter of document.execCommand() so that your editor can autocomplete the string. Keep in mind that the behavior of execCommand() is very inconsistent between browsers and there is only an unofficial draft specification. MDN even goes as far as marking the function as "deprecated".

Custom element classes (view source)

Better-TypeScript adds type checking for the static attributes and lifecycle callback functions of custom element classes.

customElements.define("my-element", class extends HTMLElement {
	constructor() {
		super();
	};
	connectedCallback() { };
	disconnectedCallback() { };
	adoptedCallback(oldDocument: Document, newDocument: Document) { };
	attributeChangedCallback(name: string, oldValue: string, newValue: string, namespace: string) { };
	formAssociatedCallback(form: HTMLFormElement) { };
	formDisabledCallback(disabled: boolean) { };
	formResetCallback() { };
	formStateRestoreCallback(newState: any, mode: string) { };
	static observedAttributes: string[] = [];
	static disabledFeatures: string[] = [];
	static formAssociated: boolean = true;
});

Callback functions (view source)

[TODO]: add description

ECMAScript stuff (view source)

Symbol keys in Object.getOwnPropertyDescriptors()

For some reason, TypeScript's standard library thinks that Object.getOwnPropertyDescriptors() returns just strings as its object keys. Better-TypeScript adds support for symbol keys.

const logOwnKeys = (object: any) => {
	const descriptors = Object.getOwnPropertyDescriptors(object);
	for (const key of Reflect.ownKeys(descriptors)) {
		console.log(key, descriptors[key]); // error without Better-TypeScript
	}
};

[TODO]: add description for Array::includes & Function::{call, apply, bind}

.getTargetRanges()

[TODO]: add description