Update README and CHANGELOG.

moll · Jul 22, 2023 · aacd49a · aacd49a
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,17 @@
+## Unreleased
+- Switches from using [JsxTransform][jsx-transform] to implementing a custom JSX compiler with the help of [Acorn][acorn], a JavaScript parsing library.
+
+  The result is almost byte-for-byte identical with the exception of a few improvements around closing-brace position. Just like JsxTransform, J6Pack retains all whitespace in the source file, so all reported line numbers match.
+
+  Switching to Acorn also adds support for ECMAScript 14 (2023) and beyond.
+
+- Adds a [Browserify][browserify] transform.
+- Adds a way to set compilation options when using `j6pack/regiser` via setting the `options` property of its export.
+
+[acorn]: https://www.npmjs.com/package/acorn
+[jsx-transform]: https://www.npmjs.com/package/jsx-transform
+[browserify]: https://browserify.org
+
 ## 1.1.0 (Jan 11, 2021)
 - Escapes ampersands (`&`) in HTML and XML attributes.  
   Previous behavior permitted using HTML entities in attributes, but it's safer to opt-in to that where necessary with `Jsx.html`:

diff --git a/README.md b/README.md
@@ -3,9 +3,9 @@ J6Pack.js
 [![NPM version][npm-badge]](https://www.npmjs.com/package/j6pack)
 [![Build status][build-badge]](https://github.com/moll/js-j6pack/actions/workflows/node.yaml)
 
-J6Pack.js is a JavaScript library that transpiles **JSX to JavaScript** _and_ can separately render **JSX to HTML**. It comes with a [Browserify][browserify] transform out of the box. It's also usable from Node.js to **render JSX on the server side** and can hook into **[Express.js][express] view rendering**. J6Pack **does not depend on React nor implements a virtual DOM**. The HTML it renders is just text, though with interpolated values securely escaped.
+J6Pack.js is a JavaScript library that compiles **JSX to JavaScript** _and_ can then render the **JSX to HTML**. You can use it to add JSX support to Node.js without build tools. Its HTML rendering is also compatible with any web framework, though it's got builtin support for **[Express.js][express]**. You can even use it client-side as the HTML rendering is ECMAScript 5 compatible. There's even a [Browserify][browserify] plugin handy for bundling.
 
-To use JSX on the backend with Node.js, you don't need an external build tool. Just let J6Pack.js handle the JSX translation transparently as you `require` or import modules.
+J6Pack **does not depend on React nor implements a virtual DOM**. The HTML it renders is just text, though with interpolated values securely escaped.
 
 J6Pack.js defaults to using [Acorn][acorn] for parsing JSX — supporting ECMAScript 14 (2023) and beyond — but you're welcome to use any [ESTree](https://github.com/estree/estree) compatible parser and invoke J6Pack.js's compiler directly.
 
@@ -24,12 +24,12 @@ Installing
 npm install j6pack
 ```
 
-J6Pack.js follows [semantic versioning](http://semver.org), so feel free to depend on its major version with something like `>= 1.0.0 < 2` (a.k.a `^1.0.0`).
+J6Pack.js follows [semantic versioning](http://semver.org), so feel free to depend on its major version with something like `>= 1 < 2` (a.k.a `^1`).
 
 
-Using J6Pack to Render HTML
----------------------------
-For just generating HTML out of JSX function calls, require J6Pack.js and call it in the style of [`React.createElement`](https://react.dev/reference/react/createElement) or [equivalent JSX-functions](https://reactjs.org/docs/jsx-in-depth.html), with the exception that children need to always be in an array.
+Rendering HTML
+--------------
+For rendering HTML out of JSX-like function calls, import J6Pack.js and call it in the style of [`React.createElement`](https://react.dev/reference/react/createElement) or [equivalent JSX-functions](https://reactjs.org/docs/jsx-in-depth.html), with the **requirement that children need to always be in an array**. If you already use a JSX compiler/transpiler, that's generally what JSX gets compiled down to.
 
 ```javascript
 var Jsx = require("j6pack")
@@ -50,10 +50,10 @@ Jsx("p", null, ["Hello, world!"]) instanceof Jsx.Html // => true
 <p>Hello, world!</p> instanceof Jsx.Html // => true
 ```
 
-To use the JSX syntax (`<p>Hello, {name}!</p>`) in JavaScript on Node.js, see below.
+To use the JSX syntax (`<p>Hello, {name}!</p>`) on Node.js without an external compiler tool, by using J6Pack for transparent compiling/transpiling, see below.
 
 ### XML
-J6Pack.js by default renders HTML5 compatible HTML. If you'd like to use it to render generic XML, for example to render an [Atom feed](https://en.wikipedia.org/wiki/Atom_(Web_standard)), you can require the XML variant:
+J6Pack.js by default renders HTML5-compatible HTML. If you'd like to use it to render generic XML, for example to render an [Atom feed](https://en.wikipedia.org/wiki/Atom_(Web_standard)), you can require the XML variant from `j6pack/xml`:
 
 ```javascript
 var Jsx = require("j6pack/xml")
@@ -105,10 +105,10 @@ Jsx("p", null, ["Hello, world!"]) instanceof Jsx.Xml // => true
 ```
 
 ### DOM Attributes and Properties
-J6Pack.js renders JSX to HTML with minimal transformations, so *use HTML attribute names, not DOM properties*. That is, to set the tag's `class` attribute, use `<p class="greeting">Hello, world!</p>` rather than `className` as you would with React. Same goes for elements' `onclick`, `<label>`s' `for`, `<input>`s' `readonly` and so on.
+J6Pack.js renders HTML with minimal transformations, so *use HTML attribute names, not DOM properties*. That is, to set the tag's `class` attribute, use `<p class="greeting">Hello, world!</p>` rather than `className` as you would with React. Same goes for elements' `onclick`, `<label>`s' `for`, `<input>`s' `readonly` and so on.
 
 ### Interpolating HTML (like `innerHTML`)
-Should you need to interpolate HTML into JSX, you can't use the `innerHTML` property (or React's [dangerouslySetInnerHTML](https://react.dev/reference/react-dom/components/common#dangerously-setting-the-inner-html)) as those live only in the DOM world, not in HTML. Instead, use the `Jsx.html` function to inject your HTML into otherwise escaped values:
+Should you need to interpolate HTML into the output, you can't use the `innerHTML` property (or React's [dangerouslySetInnerHTML](https://react.dev/reference/react-dom/components/common#dangerously-setting-the-inner-html)) as those live only in the DOM world, not in HTML. Instead, use the `Jsx.html` function to inject your HTML into otherwise escaped values:
 
 ```javascript
 var Jsx = require("j6pack")
@@ -144,7 +144,9 @@ var html = <Page title="Test Page">
 </Page>
 ```
 
-### Returning Multiple Elements (React Fragments)
+If you use another JSX compiler/transpiler than J6Pack.js, configure it to call component functions directly, rather than passing them to the factory function.
+
+### Returning Multiple Elements (Fragments)
 Occasionally you may want a custom element to return multiple elements without wrapping them in yet another element. You can do that in two ways.
 
 Return an array of elements:
@@ -183,6 +185,8 @@ var html = <div>
 </div>
 ```
 
+If you need to configure your external JSX compiler/transpiler for fragments, you can set it to emit fragments either as JavaScript arrays or as invocations of `Jsx.Fragment` like regular components (children in the 2nd argument as an array).
+
 ### ESLint
 If you use [ESLint][eslint] with the [ESLint React plugin][eslint-react] to lint your JavaScript and are getting an error about [missing `React` when using JSX](https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/react-in-jsx-scope.md), you may have to specify a pragma to inform ESLint of the JSX function used:
 
@@ -194,23 +198,93 @@ var html = <p>Hello, world!</p>
 
 A sufficiently new version of [ESLint React plugin][eslint-react] seems to also have a `pragma` setting to set the factory function once for the entire project.
 
+[eslint]: https://eslint.org/
+[eslint-react]: https://github.com/yannickcr/eslint-plugin-react
+
+
+Compiling JSX to JavaScript
+---------------------------
+In addition to rendering HTML, J6Pack.js is also a compiler/transpiler for JSX syntax. If you're looking to use JSX under Node.js, see the next section. This section covers the use of the standalone compiler.
+
+To compile a string of JavaScript with JSX into plain JavaScript, import the J6Pack.js compiler and invoke it with the source code
+
+```javascript
+var compile = require("./compiler")
+
+var js = compile(`
+  var Jsx = require("j6pack")
+  var html = <Greeting name="John" />
+
+  function Greeting(attrs) {
+    return <h1 class="greeting">Hello, {attrs.name}!</h1>
+  }
+`)
+```
+
+The `js` variable should then include the compiled/transpiled output:
+
+```js
+var Jsx = require("j6pack")
+var html = Greeting({name: "John"})
+
+function Greetng(attrs) {
+  return Jsx("h1", {class: "greeting"}, ["Hello, ", attrs.name, "!"])
+}
+```
+
+### Using a Different JavaScript Parser
+J6Pack.js defaults to using [Acorn][acorn] for parsing JSX — supporting ECMAScript 14 (2023) and beyond — but you're welcome to use any [ESTree](https://github.com/estree/estree) compatible parser that also supports JSX AST nodes.
+
+For example, use of [Esprima][esprima] should be something like:
+
+```js
+var parse = require("esprima").parse
+var compile = require("j6pack/compiler").compile
 
-Using J6Pack to Render JSX to JavaScript
-----------------------------------------
-### Node.js
-To add support for JSX syntax to Node.js, require `j6pack/register` before starting the app:
+var ast = parse(`
+  var Jsx = require("j6pack")
+  var html = <h1 class="greeting">Hello, John!</h1>
+`)
+
+compile(ast)
+```
+
+### Options
+The compiler has a few options to customize its output.
+
+Option | Description
+-------|------------
+`factory` | The function called for creating elements.<br>Called with the tag name, attributes object or `null`, and an array of children.<br>Defaults to `Jsx`.
+`fragmentFactory` | The function called for `<>…</>` JSX syntax.<br>Called with `null` and an array of children.<br>Set to `null` if want a plain JavaScript array instead of a function call.<br>Defaults to `null`.
+`componentFactory` | The function called for component element (tags whose name starts with a capitalized letter).<br>Called with the component variable, attributes object or `null`, and an array of children.<br>Set to `null` if you want the component variable called directly with attributes and children.<br>Defaults to `null`.
+`assign` | The function used for merging spread attributes (`<div {...attrs} class="foo" />`).<br>Defaults to `Object.assign`.
+`ecmaVersion` | Set or limit the JavaScript version for parsing. Useful for ensuring you don't accidentally use newer JavaScript syntax in your source files.<br>[Acorn][acorn], the parser J6Pack.js uses by default, supports versions from 3–14 and beyond.<br>Defaults to `"latest"`.
+`sourceType` | Set to `script` or `module` to configure support for `import` and `export` declarations.<br>Defaults to `script` if `ecmaVersion` is 3 or 5, `module` otherwise.
+
+### Executable
+J6Pack.js comes with a simple executable, `j6pack` that you can use to precompile JSX, perhaps for testing or just seeing what JSX compiles down to. After installing J6Pack.js, invoke it with `./node_modules/.bin/j6pack` or from `bin/j6pack` from this repository:
+
+```sh
+cat views/index_page.jsx | ./node_modules/.bin/j6pack
+./node_modules/.bin/j6pack views/index_page.jsx
+```
+
+
+Using JSX with Node.js
+----------------------
+To add transparent support for importing JSX source files to Node.js, require `j6pack/register` before starting the app:
 
 ```sh
 node --require j6pack/register app.js
 ```
 
-Or require it in your main entry file before you load `.jsx` files:
+Or `require` it in your main entry file before you load `.jsx` files:
 
 ```javascript
 require("j6pack/register")
 ```
 
-Then you can write JSX anywhere in `.jsx` files and render HTML, for example, from within your request handlers:
+Then, combined with J6Pack.js's HTML rendering, you can use JSX to respond with HTML from within your request handlers:
 
 ```javascript
 var Jsx = require("j6pack")
@@ -230,23 +304,6 @@ Http.createServer(handleRequest).listen(process.env.PORT || 3000)
 
 The same example code is in `examples/server.jsx` which you can run via `make examples/server.jsx` and view on <http://localhost:3000> by default.
 
-### Browserify
-To have [Browserify][browserify] use J6Pack.js for precompiling JSX files to JavaScript, pass `j6pack/browserify` as a transform when invoking Browserify:
-
-```sh
-browserify --extension=jsx --transform j6pack/browserify
-```
-
-Or add a `browserify` property to `package.json`:
-
-```json
-{
-	"browserify": {
-		"transform": ["j6pack/browserify"]
-	}
-}
-```
-
 ### Express.js
 J6Pack.js comes with explicit support for the [Express.js][express] web framework [templates](https://expressjs.com/en/guide/using-template-engines.html). To add `.jsx` template support to Express.js, set it as an engine:
 
@@ -316,25 +373,35 @@ app.get("/", function(_req, res) {
 ```
 
 ### Renaming the `Jsx` Function
-By default the transpiled JavaScript expects the name of the JSX-render (factory) function to be `Jsx`. That's why all the examples here assign `require("j6pack")` to `Jsx`. If you want to use a different function name, feel free to either use the `@jsx` pragma or make a local copy of `j6pack/register` for use in Node.js.
+By default the compiled JavaScript expects the name of the JSX-render (factory) function to be `Jsx`. That's why all the examples here assign `require("j6pack")` to `Jsx`. If you want to use a different function name, you've got three options:
 
-```javascript
-/** @jsx Jaysex */
-var Jaysex = require("j6pack")
-var html = <p>Hello, world!</p>
-```
+1. Use the `@jsx` pragma to set the factory function:
 
-Or run the following JavaScript at the start of the your app (just like `require`ing `j6pack/register` does):
+   ```javascript
+   /** @jsx Jaysex */
+   var Jaysex = require("j6pack")
+   var html = <p>Hello, world!</p>
+   ```
 
-```javascript
-var Fs = require("fs")
-var compile = require("./compiler")
+2. Set the `options` on the export of `j6pack/register` before you `require` any `.jsx` files:
 
-require.extensions[".jsx"] = function(module, path) {
-  var source = Fs.readFileSync(path, "utf8")
-  module._compile(compile(source, {factory: "Jaysex"}), path)
-}
-```
+   ```javascript
+   require("j6pack/register").options = {factory: "Jaysex"}
+   ```
+
+3. Copy the contents of `j6pack/register` to your own project and invoke the `compile` function with options directly:
+
+   ```javascript
+   var Fs = require("fs")
+   var compile = require("./compiler")
+
+   require.extensions[".jsx"] = function(module, path) {
+     var source = Fs.readFileSync(path, "utf8")
+     module._compile(compile(source, {factory: "Jaysex"}), path)
+   }
+   ```
+
+See above for a [list of all options][#options].
 
 ### Renaming `Object.assign` for Spread Attributes
 Spread attributes get compiled down to using `Object.assign`. For example, the following:
@@ -351,16 +418,44 @@ Jsx("input", Object.assign({}, defaults, {name: "email"}, attrs))
 
 If for some reason you wish to not depend on `Object.assign`, you can use the `assign` option when compiling to replace `Object.assign` with a function name of your own. Works the same as above with changing the `factory` function name.
 
-### Executable
-J6Pack.js comes with a simple executable, `j6pack` that you can use to precompile JSX, perhaps for testing or just seeing what JSX transpiles down to. After installing J6Pack.js, invoke it with `./node_modules/.bin/j6pack` or from `bin/j6pack` from this repository:
+Both the HTML (`require("j6pack/html")`) and XML (`require("j6pack/xml")`) renderers have an `assign` export with a helper function that shallow-merges objects. If you can't depend on Object.assign being available (e.g. in old browsers) or you dislike its ignoring of inherited properties, you're welcome to set the `assign` option to `Jsx.assign`.
+
+
+Compiling JSX to JavaScript with Browserify
+-------------------------------------------
+To have [Browserify][browserify] use J6Pack.js for precompiling JSX files to JavaScript, pass `j6pack/browserify` as a transform when invoking Browserify:
 
 ```sh
-cat views/index_page.jsx | ./node_modules/.bin/j6pack
-./node_modules/.bin/j6pack views/index_page.jsx
+browserify --extension=jsx --transform j6pack/browserify
 ```
 
-[eslint]: https://eslint.org/
-[eslint-react]: https://github.com/yannickcr/eslint-plugin-react
+Or add a `browserify` property to `package.json`:
+
+```json
+{
+	"browserify": {
+		"transform": ["j6pack/browserify"]
+	}
+}
+```
+
+### Setting Options
+To set compiler options, use the Browserify transform option syntax. For example, to limit J6Pack.js's JavaScript parser to ECMAScript 5 (to prevent accidentally using newer JavaScript syntax in your source files):
+
+
+```sh
+browserify --extension=jsx --transform [ j6pack/browserify --ecmaVersion 5 ]
+```
+
+Or via the `browserify` property in `package.json`:
+
+```json
+{
+	"browserify": {
+		"transform": [["j6pack/browserify", {"ecmaVersion": "5"}]]
+	}
+}
+```
 
 
 License