🏷 Typed querySelector

querySelector and querySelectorAll functions with better typing by leveraging TypeScript 4.1 template literal type.

💿 Install

npm i -D typed-query-selector

🍉 Usage

Automatic shim

All you need to do is to import this module, then the querySelector and querySelectorAll function will be enhanced.

This module only works at type level and doesn't have any runtime code.

import 'typed-query-selector'

document.querySelector('div#app') // ==> HTMLDivElement

document.querySelector('div#app > form#login') // ==> HTMLFormElement

document.querySelectorAll('span.badge') // ==> NodeListOf<HTMLSpanElement>

anElement.querySelector('button#submit') // ==> HTMLButtonElement

If you aren't going to use ES Modules you can modify your tsconfig.json, however this is NOT recommended, unless you know what you're doing.

{
  "compilerOptions": {
    "types": ["typed-query-selector"]
  }
}

Strict mode

Available in v2.3+

In strict mode, the selector parser will do additional syntax checks on input string. If there're syntax errors, return type will be never instead of Element.

Example usage:

import 'typed-query-selector/strict'

const element = document.querySelector('div[test') // return `never`

This feature won't be enabled by default and you can opt-in. If you want to enable this, change import entry:

- import 'typed-query-selector'
+ import 'typed-query-selector/strict'

That's all. If you pass an invalid selector, because it returns never, TypeScript will prevent you from accessing properties/methods on element or using element at somewhere.

Note that it doesn't guarantee that it can detect every kind of syntax errors, since such parser will become very complex and compilation performance may go bad.

Use the parser

If you just want to use the selector parser itself, we've exported for you:

import type { ParseSelector } from 'typed-query-selector/parser'

type MyElement = ParseSelector<'form#login'>

Please note that you should import typed-query-selector/parser, not typed-query-selector. This is safe because this import doesn't patch to the querySelector and querySelectorAll function.

Sometimes, you may want to specify another fallback type (such as HTMLElement, not default Element type) when failed to parse selector or failed to look up, you can pass a fallback type as the second type parameter:

Available in v2.4+

import type { ParseSelector } from 'typed-query-selector/parser'

type MyElement = ParseSelector<'unknown-tag', HTMLElement> // ==> HTMLElement

💡 Supported Use Cases

With class, ID, pseudo class or attribute

import 'typed-query-selector'

document.querySelector('div.container') // ==> HTMLDivElement

document.querySelector('div#app') // ==> HTMLDivElement

document.querySelector('input[name=username]') // ==> HTMLInputElement

document.querySelector('input:first-child') // ==> HTMLInputElement

Even mix them:

import 'typed-query-selector'

document.querySelector('input.form-control[name=username]') // ==> HTMLInputElement

Combinators

import 'typed-query-selector'

document.querySelector('body div') // ==> HTMLDivElement

document.querySelector('body > form') // ==> HTMLFormElement

document.querySelector('h1 + p') // ==> HTMLParagraphElement

document.querySelector('h2 ~ p') // ==> HTMLParagraphElement

Grouping selectors

import 'typed-query-selector'

document.querySelector('div, span') // ==> HTMLDivElement | HTMLSpanElement

Fallback

Web Components

If you passed an unknown tag, it will fall back to Element, but you can override it by specifying concrete type.

import 'typed-query-selector'

document.querySelector('my-web-component') // ==> Element

document.querySelector<MyComponent>('my-web-component') // ==> MyComponent

Invalid selector

When passing an invalid selector which causes parsing error, it will fall back to Element.

import 'typed-query-selector'

document.querySelector('div#app >') // ==> Element

document.querySelector('div#app ?') // ==> Element

However, if you're using strict mode, all querySelector calls above will return never type. This can stop you from misusing it.

import 'typed-query-selector/strict'

const el = document.querySelector('div#app >')
el.className // TypeScript will report error when compiling

🔩 Technical Details

Why returns never in strict mode?

In runtime, if you pass an invalid selector string to querySelector or querySelectorAll function, it will throw an error instead of returning null or undefined or anything else. For details, please read TypeScript Handbook.

🔗 Related

• Type Gymnastics - Collection of wonderful TypeScript type gymnastics code snippets.

📃 License

MIT License

Copyright (c) 2020-present Pig Fang