如何不使用react，也能解析jsx？

原文自定义jsx解析工厂函数

问题

我们通常会在react项目中使用jsx，当我们习惯了jsx的语法之后，可能就脱离不开jsx了，如果我们不在react而是在一个原生js项目中也想使用jsx怎么办呢？

解决方案

react官方已经出了一个新的jsx解析器，剥离了jsx-runtime用来单独解析jsx，可以脱离react使用jsx，并且和babel、typescript官方合作，使用babel或者ts配置即可解析jsx，都提供了简洁的配置方案。或者，我们还可以自定义一个jsx解析函数。

方案一：Babel配置

1. 先安装依赖包

npm update @babel/core @babel/preset-react

2. 再配置babel.config.json文件

{
  "presets": [
    ["@babel/preset-react", {
      "runtime": "automatic"
    }]
  ]
}

方案二：typescript配置

要在ts中使用jsx，即使用tsx。Typescript 4.1 支持 React 17的jsx和jsxs工厂函数的tsconfig.json配置

• 开发环境下用 "jsx":"react-jsxdev"
• 生产环境下用 "jsx":"react-jsx"
  比如：

// ./src/tsconfig.json
{
    "compilerOptions": {
        "module": "esnext",
        "target": "es2015",
        "jsx": "react-jsx",
        "strict": true
    },
    "include": [
        "./**/*"
    ]
}

方案三：自定义tsx工厂函数

自定义一套jsx解析工厂函数，可以了解jsx的解析过程。下面演示一个ts版本的tsx解析函数。

1. 先定义一个jsxFactory.ts用作定义和导出工厂函数

// --- jsxFactory.ts ---
/* https://gist.github.com/borestad/eac42120613bc67a3714f115e8b485a7
 * Custom jsx parser
 * See: tsconfig.json
 *
 *   {
 *     "jsx": "react",
 *     "jsxFactory": "h",
 *     "lib": [
 *       "es2017",
 *       "dom",
 *       "dom.iterable"
 *     ]
 *   }
 *
 */
interface entityMapData {
  [key: string]: string;
}
export const entityMap: entityMapData = {
  "&": "amp",
  "<": "lt",
  ">": "gt",
  '"': "quot",
  "'": "#39",
  "/": "#x2F",
};

export const escapeHtml = (str: object[] | string) =>
  String(str).replace(/[&<>"'\/\\]/g, (s) => `&${entityMap[s]};`);

// To keep some consistency with React DOM, lets use a mapper
// https://reactjs.org/docs/dom-elements.html
export const AttributeMapper = (val: string) =>
  ({
    tabIndex: "tabindex",
    className: "class",
    readOnly: "readonly",
  }[val] || val);

// tslint:disable-next-line:no-default-export
export function DOMcreateElement(
  tag: Function | string,
  attrs?: { [key: string]: any },
  ...children: (HTMLElement | string)[]
): HTMLElement {
  attrs = attrs || {};
  const stack: any[] = [...children];

  // Support for components(ish)
  if (typeof tag === "function") {
    attrs.children = stack;
    return tag(attrs);
  }

  const elm = document.createElement(tag);

  // Add attributes
  for (let [name, val] of Object.entries(attrs)) {
    name = escapeHtml(AttributeMapper(name));
    if (name.startsWith("on") && name.toLowerCase() in window) {
      elm.addEventListener(name.toLowerCase().substr(2), val);
    } else if (name === "ref") {
      val(elm);
    } else if (name === "style") {
      Object.assign(elm.style, val);
    } else if (val === true) {
      elm.setAttribute(name, name);
    } else if (val !== false && val != null) {
      elm.setAttribute(name, escapeHtml(val));
    } else if (val === false) {
      elm.removeAttribute(name);
    }
  }

  // Append children
  while (stack.length) {
    const child = stack.shift();

    // Is child a leaf?
    if (!Array.isArray(child)) {
      elm.appendChild(
        (child as HTMLElement).nodeType == null
          ? document.createTextNode(child.toString())
          : child
      );
    } else {
      stack.push(...child);
    }
  }

  return elm;
}

export const DOMcreateFragment = (
  attrs?: { [key: string]: any },
  ...children: (HTMLElement | string)[]
): (HTMLElement | string)[] => {
  return children;
};

2. 配套的工厂函数d.ts声明文件

// --- jsxFactory.d.ts ---
declare namespace JSX {
  type Element = string;
  interface IntrinsicElements {
    [eleName: string]: any;
  }
}

3. 然后在tsconfig.json中加上jsx配置

{
    "compilerOptions":{
        // ...其他配置
        "jsx": "preserve",
        "jsxFactory": "DOMcreateElement",
        "jsxFragmentFactory": "DOMcreateFragment",
    }
    
}

比如下面这个参考

{
  "compilerOptions": {
    "rootDir": "src",
    "outDir": "lib",
    "target": "ESNext",
    "useDefineForClassFields": true,
    "module": "ESNext",
    "lib": ["ESNext", "dom", "dom.iterable"],
    "moduleResolution": "Node",
    "strict": true,
    "sourceMap": true,
    "resolveJsonModule": true,
    "esModuleInterop": true,
    "noEmit": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true,
    "declaration": true,
    "declarationDir": "./lib",
    "declarationMap": true,
    "baseUrl": "./",
    "jsx": "preserve",
    "jsxFactory": "DOMcreateElement",
    "jsxFragmentFactory": "DOMcreateFragment",
    "allowJs": true
  },
  "include": ["./src"]
}

4. 通常来说这样就可以使用了，在每一个.tsx结尾的文件中引入DOMcreateElement即可，但是如果你用的esbuild，你还可以在esbuild配置中自动注入DOMcreateElement和DOMcreateFragment

一个参考的esbuild配置，下面示例中@/helper/jsxFactory是jsxFactory.ts所在目录

esbuild: {
    jsxFactory: "DOMcreateElement",
    jsxFragment: "DOMcreateFragment",
    jsxInject: `import { DOMcreateElement, DOMcreateFragment } from '@/helper/jsxFactory';`,
}

方案四：简洁的jsx工厂函数

jsx简洁版本，可以依照这个简单版本做定制和扩展

版本一

const appendChild = (parent, child) => {
  if (Array.isArray(child))
    child.forEach((nestedChild) => appendChild(parent, nestedChild));
  else
    parent.appendChild(child.nodeType ? child : document.createTextNode(child));
};

export const DOMcreateElement = (tag, props, ...children) => {
  if (typeof tag === 'function') return tag(props, children);

  const element = document.createElement(tag);

  Object.entries(props || {}).forEach(([name, value]) => {
    if (name.startsWith('on') && name.toLowerCase() in window) {
      element.addEventListener(name.toLowerCase().substr(2), value);
    } else {
      element[name] = value;
      // element.setAttribute(name, value.toString());
    }
  });

  children.forEach((child) => {
    appendChild(element, child);
  });

  return element;
};

export const DOMcreateFragment = (props, ...children) => {
  return children;
};

版本二

/**
 * A helper function that ensures we won't work with null values
 * @param val
 * @param fallback
 */
function nonNull(val, fallback) {
  return Boolean(val) ? val : fallback;
}

/**
 * How do we handle children. Children can either be:
 * 1. Calls to DOMcreateElement, return a Node
 * 2. Text content, returns a Text
 * @param children
 */

function DOMparseChildren(children) {
  return children.map((child) => {
    if (typeof child === 'string') {
      return document.createTextNode(child);
    }

    return child;
  });
}

/**
 * How do we handle regular nodes.
 * 1. We create an element
 * 2. We apply all properties from JSX to this DOM node
 * 3. If available,we append all children.
 * @param element
 * @param properties
 * @param children
 */

function DOMparseNode(element, properties, children) {
  const el = document.createElement(element);
  Object.keys(nonNull(properties, {})).forEach((key) => {
    el[key] = properties[key];
  });

  DOMparseChildren(children).forEach((child) => {
    el.appendChild(child);
  });

  return el;
}

/**
 * Our entry function.
 * 1. Is the element a function,than it's a functional component.
 *    We call this function (pass props and children of course)
 *    and return the result.We expect a return value of type Node
 * 2. If the element is a string, we parse a regular node
 * @param element
 * @param properties
 * @param children
 */

export function DOMcreateElement(element, properties, ...children) {
  if (typeof element === 'function') {
    return element({
      ...nonNull(properties, {}),
      children,
    });
  }

  return DOMparseNode(element, properties, children);
}

原文自定义jsx解析工厂函数

参考

• 介绍全新的 JSX 转换
• React 17 JSX Factories
• Build your own React
• You don’t need React to use JSX