g-plane
🏷 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') // ==> HTMLButtonElementThe example above assumes you're using bundlers or build tools with transpilers,
however, sometimes this may not match your situation.
For example, running tsc or Babel out of bundlers.
In this case, you can import this library like this:
import type {} from 'typed-query-selector'
document.querySelector('div#app') // ==> HTMLDivElementThis looks ugly but it works.
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 perform 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,
StrictlyParseSelector, // or use the strict parser
} 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') // ==> HTMLInputElementEven mix them:
import 'typed-query-selector'
document.querySelector('input.form-control[name=username]') // ==> HTMLInputElementAnd with :is() or :where():
Available in v2.5+
import 'typed-query-selector'
document.querySelector(':is(div#id, span.class[k=v])') // ==> HTMLDivElement | HTMLSpanElement
document.querySelector(':where(div#id, span.class[k=v])') // ==> HTMLDivElement | HTMLSpanElementCombinators
import 'typed-query-selector'
document.querySelector('body div') // ==> HTMLDivElement
document.querySelector('body > form') // ==> HTMLFormElement
document.querySelector('h1 + p') // ==> HTMLParagraphElement
document.querySelector('h2 ~ p') // ==> HTMLParagraphElementGrouping selectors
import 'typed-query-selector'
document.querySelector('div, span') // ==> HTMLDivElement | HTMLSpanElementFallback
Custom Elements
If you passed an unknown tag, it will fall back to Element.
import 'typed-query-selector'
document.querySelector('my-web-component') // ==> ElementHowever, you can override it by specifying a concrete type as a type argument.
document.querySelector<MyComponent>('my-web-component') // ==> MyComponentAlternatively, you can use global augmentation and interface merging to extend HTMLElementTagNameMap with your custom elements.
declare global {
interface HTMLElementTagNameMap {
'my-web-component': MyComponent
}
}
document.querySelector('my-web-component') // ==> MyComponentInvalid 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 ?') // ==> ElementHowever, 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