react源码层深入刨析babel解析jsx实现

<div className='box'>
<h1 className='title' style={{'color':'red'}}>React源码解析</h1>
<ul>
<li>第一章</li>
<li>第二章</li>
<li>第三章</li>
<li>第四章</li>
</ul>
</div>

// packages/react/src/jsx/ReactJSX.js
import {REACT_FRAGMENT_TYPE} from 'shared/ReactSymbols';
import {
jsxWithValidationStatic,
jsxWithValidationDynamic,
jsxWithValidation,
} from './ReactJSXElementValidator';
import {jsx as jsxProd} from './ReactJSXElement';
const jsx = __DEV__ ? jsxWithValidationDynamic : jsxProd;
const jsxs = __DEV__ ? jsxWithValidationStatic : jsxProd;
const jsxDEV = __DEV__ ? jsxWithValidation : undefined;
export {REACT_FRAGMENT_TYPE as Fragment, jsx, jsxs, jsxDEV};

export function jsx(type, config, maybeKey) {
let propName;
//标签上的属性集合
const props = {};
//单独处理key ref
let key = null;
let ref = null;
if (maybeKey !== undefined) {
key = '' + maybeKey;
}
if (hasValidKey(config)) {
// 处理合法的key
key = '' + config.key;
}
if (hasValidRef(config)) {
// 处理合法的ref
ref = config.ref;
}
// 把属性加到props中
for (propName in config) {
if (
hasOwnProperty.call(config, propName) &&
!RESERVED_PROPS.hasOwnProperty(propName)
) {
props[propName] = config[propName];
}
}
// 处理默认props
if (type && type.defaultProps) {
const defaultProps = type.defaultProps;
for (propName in defaultProps) {
if (props[propName] === undefined) {
props[propName] = defaultProps[propName];
}
}
}
return ReactElement(
type,
key,
ref,
undefined,
undefined,
ReactCurrentOwner.current,
props
)
}

const ReactElement = function(type, key, ref, self, source, owner, props) {
const element = {
// 表示是否为ReactElement
$$typeof: REACT_ELEMENT_TYPE,
// 元素自身属性
type: type,
key: key,
ref: ref,
props: props,
// Record the component responsible for creating this element.
_owner: owner,
};
if (__DEV__) {
element._store = {};
// 开发环境下将_store、_self、_source属性变为不可枚举
Object.defineProperty(element._store, 'validated', {
configurable: false,
enumerable: false,
writable: true,
value: false,
});
Object.defineProperty(element, '_self', {
configurable: false,
enumerable: false,
writable: false,
value: self,
});
Object.defineProperty(element, '_source', {
configurable: false,
enumerable: false,
writable: false,
value: source,
});
// 冻结props、element防止被手动修改
if (Object.freeze) {
Object.freeze(element.props);
Object.freeze(element);
}
}
return element;
};

// packages/react/src/ReactElement.js
export function createElement(type, config, children) {
let propName;
// 记录标签上的属性集合
const props = {};
//单独处理key ref
let key = null;
let ref = null;
let self = null;
let source = null;
// 当config部位null的时候，表示标签上有属性，加到props里面去
if (config != null) {
// 合法的ref才做处理
if (hasValidRef(config)) {
ref = config.ref;
if (__DEV__) {
warnIfStringRefCannotBeAutoConverted(config);
}
}
if (hasValidKey(config)) {
// 有合法的key才做处理
key = '' + config.key;
}
// 记录信息用于debug
self = config.__self === undefined ? null : config.__self;
source = config.__source === undefined ? null : config.__source;
// 处理self，source，key，ref以外的属性，加入props中
for (propName in config) {
if (
hasOwnProperty.call(config, propName) &&
!RESERVED_PROPS.hasOwnProperty(propName)
) {
props[propName] = config[propName];
}
}
}
// 处理子节点
const childrenLength = arguments.length - 2;
// 单标签子节点
if (childrenLength === 1) {
props.children = children;
//嵌套子节点
} else if (childrenLength > 1) {
const childArray = Array(childrenLength);
for (let i = 0; i < childrenLength; i++) {
childArray[i] = arguments[i + 2];
}
//开发环境冻结，childArray防止被修改
if (__DEV__) {
if (Object.freeze) {
Object.freeze(childArray);
}
}
props.children = childArray;
}
// 处理默认props
if (type && type.defaultProps) {
const defaultProps = type.defaultProps;
for (propName in defaultProps) {
if (props[propName] === undefined) {
props[propName] = defaultProps[propName];
}
}
}
if (__DEV__) {
// dev环境下，key 与 ref不挂到props中去
if (key || ref) {
const displayName =
typeof type === 'function'
? type.displayName || type.name || 'Unknown'
: type;
if (key) {
defineKeyPropWarningGetter(props, displayName);
}
if (ref) {
defineRefPropWarningGetter(props, displayName);
}
}
}
// 调用返回
return ReactElement(
type,
key,
ref,
self,
source,
ReactCurrentOwner.current,
props,
);
}

const ReactElement = function(type, key, ref, self, source, owner, props) {
const element = {
// This tag allows us to uniquely identify this as a React Element
$$typeof: REACT_ELEMENT_TYPE,
// Built-in properties that belong on the element
type: type,
key: key,
ref: ref,
props: props,
// Record the component responsible for creating this element.
_owner: owner,
};
if (__DEV__) {
// The validation flag is currently mutative. We put it on
// an external backing store so that we can freeze the whole object.
// This can be replaced with a WeakMap once they are implemented in
// commonly used development environments.
element._store = {};
// To make comparing ReactElements easier for testing purposes, we make
// the validation flag non-enumerable (where possible, which should
// include every environment we run tests in), so the test framework
// ignores it.
Object.defineProperty(element._store, 'validated', {
configurable: false,
enumerable: false,
writable: true,
value: false,
});
// self and source are DEV only properties.
Object.defineProperty(element, '_self', {
configurable: false,
enumerable: false,
writable: false,
value: self,
});
// Two elements created in two different places should be considered
// equal for testing purposes and therefore we hide it from enumeration.
Object.defineProperty(element, '_source', {
configurable: false,
enumerable: false,
writable: false,
value: source,
});
if (Object.freeze) {
Object.freeze(element.props);
Object.freeze(element);
}
}
return element;
};

// packages/react/src/ReactBaseClasses.js
function Component(props, context, updater) {
// 接受各种参数,挂到this上
this.props = props;
this.context = context;
this.refs = emptyObject;
// updater ??
this.updater = updater || ReactNoopUpdateQueue;
}
// 原型上挂载了isReactComponent用来区分函数组件与类组件
Component.prototype.isReactComponent = {};
//原型上挂载了setState方法用来触发更新
Component.prototype.setState = function(partialState, callback) {
invariant(
typeof partialState === 'object' ||
typeof partialState === 'function' ||
partialState == null,
'setState(...): takes an object of state variables to update or a ' +
'function which returns an object of state variables.',
);
// 调用updater上的enqueueSetState方法？？？
this.updater.enqueueSetState(this, partialState, callback, 'setState');
};
// 原型上挂载了强制更新的方法
Component.prototype.forceUpdate = function(callback) {
this.updater.enqueueForceUpdate(this, callback, 'forceUpdate');
};