path: packages/react-reconciler/src/ReactFiberLazyComponent.js

resolveDefaultProps

解析默认 props

export function resolveDefaultProps(Component: any, baseProps: Object): Object {if (Component && Component.defaultProps) {// 解析默认 props。取自 ReactElementconst props = Object.assign({}, baseProps);const defaultProps = Component.defaultProps;// 对未传入的 props 附上默认值for (let propName in defaultProps) {if (props[propName] === undefined) {props[propName] = defaultProps[propName];}}return props;}return baseProps;
}
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React 解析默认 props 的方式就是在组件上寻找是否存在 defaultProps 属性。如果存在则对它进行遍历，拷贝当前未指定的 prop。

readLazyComponentType

export function readLazyComponentType<T>(lazyComponent: LazyComponent<T>): T {const status = lazyComponent._status;const result = lazyComponent._result;switch (status) {case Resolved: {const Component: T = result;return Component;}case Rejected: {const error: mixed = result;throw error;}case Pending: {const thenable: Thenable<T, mixed> = result;throw thenable;}default: {lazyComponent._status = Pending;const ctor = lazyComponent._ctor;const thenable = ctor();thenable.then(moduleObject => {if (lazyComponent._status === Pending) {const defaultExport = moduleObject.default;if (__DEV__) {// do something}lazyComponent._status = Resolved;lazyComponent._result = defaultExport;}},error => {if (lazyComponent._status === Pending) {lazyComponent._status = Rejected;lazyComponent._result = error;}},);// Handle synchronous thenables.switch (lazyComponent._status) {case Resolved:return lazyComponent._result;case Rejected:throw lazyComponent._result;}lazyComponent._result = thenable;throw thenable;}}
}
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