estree-util-build-jsx
estree utility to turn JSX into function calls: <x /> -> h('x')!
Contents
What is this?
This package is a utility that takes an estree (JavaScript) syntax tree as input that contains embedded JSX nodes (elements, fragments) and turns them into function calls.
When should I use this?
If you already have a tree and only need to compile JSX away, use this. If you have code, use something like SWC or esbuild instead.
Install
This package is ESM only. In Node.js (version 16+), install with npm:
npm install estree-util-build-jsx
In Deno with esm.sh:
import {buildJsx} from 'https://esm.sh/estree-util-build-jsx@3'
In browsers with esm.sh:
<script type="module">
import {buildJsx} from 'https://esm.sh/estree-util-build-jsx@3?bundle'
</script>
Use
Say we have the following example.jsx:
import x from 'xastscript'
console.log(
<album id={123}>
<name>Born in the U.S.A.</name>
<artist>Bruce Springsteen</artist>
<releasedate date="1984-04-06">April 6, 1984</releasedate>
</album>
)
console.log(
<>
{1 + 1}
<self-closing />
<x name key="value" key={expression} {...spread} />
</>
)
…and next to it a module example.js:
import fs from 'node:fs/promises'
import jsx from 'acorn-jsx'
import {fromJs} from 'esast-util-from-js'
import {buildJsx} from 'estree-util-build-jsx'
import {toJs} from 'estree-util-to-js'
const doc = String(await fs.readFile('example.jsx'))
const tree = fromJs(doc, {module: true, plugins: [jsx()]})
buildJsx(tree, {pragma: 'x', pragmaFrag: 'null'})
console.log(toJs(tree).value)
…now running node example.js yields:
import x from "xastscript";
console.log(x("album", {
id: 123
}, x("name", null, "Born in the U.S.A."), x("artist", null, "Bruce Springsteen"), x("releasedate", {
date: "1984-04-06"
}, "April 6, 1984")));
console.log(x(null, null, 1 + 1, x("self-closing"), x("x", Object.assign({
name: true,
key: "value",
key: expression
}, spread))));
API
This package exports the identifier buildJsx. There is no default export.
buildJsx(tree[, options])
Turn JSX in tree into function calls: <x /> -> h('x')!
Algorithm
In almost all cases, this utility is the same as the Babel plugin, except that they work on slightly different syntax trees.
Some differences:
- no pure annotations things
this is not a component: <this> -> h('this'), not h(this)- namespaces are supported:
<a:b c:d> -> h('a:b', {'c:d': true}), which throws by default in Babel or can be turned on with throwIfNamespace - no
useSpread, useBuiltIns, or filter options
Parameters
tree (Node) — tree to transform (typically Program)options (Options, optional) — configuration
Returns
Nothing (undefined).
Options
Configuration (TypeScript type).
👉 Note: you can also configure runtime, importSource, pragma, and pragmaFrag from within files through comments.
Fields
runtime
Choose the runtime (Runtime, default: 'classic').
Comment form: @jsxRuntime theRuntime.
importSource
Place to import jsx, jsxs, jsxDEV, and Fragment from, when the effective runtime is automatic (string, default: 'react').
Comment form: @jsxImportSource theSource.
👉 Note: /jsx-runtime or /jsx-dev-runtime is appended to this provided source. In CJS, that can resolve to a file (as in theSource/jsx-runtime.js), but for ESM an export map needs to be set up to point to files:
// …
"exports": {
// …
"./jsx-runtime": "./path/to/jsx-runtime.js",
"./jsx-dev-runtime": "./path/to/jsx-runtime.js"
// …
pragma
Identifier or member expression to call when the effective runtime is classic (string, default: 'React.createElement').
Comment form: @jsx identifier.
pragmaFrag
Identifier or member expression to use as a symbol for fragments when the effective runtime is classic (string, default: 'React.Fragment').
Comment form: @jsxFrag identifier.
development
When in the automatic runtime, whether to import theSource/jsx-dev-runtime.js, use jsxDEV, and pass location info when available (boolean, default: false).
This helps debugging but adds a lot of code that you don’t want in production.
filePath
File path to the original source file (string, example: 'path/to/file.js'). Passed in location info to jsxDEV when using the automatic runtime with development: true.
Runtime
How to transform JSX (TypeScript type).
Type
type Runtime = 'automatic' | 'classic'
Examples
Example: use with Acorn
To support configuration from comments in Acorn, those comments have to be in the program. This is done by espree but not automatically by acorn:
import {Parser} from 'acorn'
import jsx from 'acorn-jsx'
const doc = '' // To do: get `doc` somehow.
const comments = []
const tree = Parser.extend(jsx()).parse(doc, {onComment: comments})
tree.comments = comments
Types
This package is fully typed with TypeScript. It exports the additional type Options and Runtime.
Compatibility
Projects maintained by the unified collective are compatible with maintained versions of Node.js.
When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, estree-util-build-jsx@^3, compatible with Node.js 16.
Security
This package is safe.
Contribute
See contributing.md in syntax-tree/.github for ways to get started. See support.md for ways to get help.
This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.
License
MIT © Titus Wormer