這篇文章將為大家詳細講解有關(guān)React首次渲染中batchedMountComponentIntoNode做了什么，小編覺得挺實用的，因此分享給大家做個參考，希望大家閱讀完這篇文章后可以有所收獲。
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本文將要講解的調(diào)用棧是下面這個樣子的：
|=ReactMount.render(nextElement, container, callback) ___ |=ReactMount._renderSubtreeIntoContainer() | |-ReactMount._renderNewRootComponent() | |-instantiateReactComponent() | |~batchedMountComponentIntoNode() upper half |~mountComponentIntoNode() (平臺無關(guān)) |-ReactReconciler.mountComponent() | |-ReactCompositeComponent.mountComponent() | |-ReactCompositeComponent.performInitialMount() | |-instantiateReactComponent() _|_ |-ReactDOMComponent.mountComponent() lower half |-_mountImageIntoNode() (HTML DOM 相關(guān)) _|_
如果看源碼，我們會留意到很多transaction相關(guān)的代碼，我們暫時先將其忽略，會在后續(xù)的文章中進行講解。暫時可以理解為調(diào)用transaction.perform時，實際上就是對第一個參數(shù)進行函數(shù)調(diào)用。跳過一些模版代碼后，實際上做事情的是 mountComponentIntoNode 這個方法。
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重慶分公司
// 文件位置：src/renderers/dom/client/ReactMount.js
function mountComponentIntoNode(
wrapperInstance, // ReactCompositeComponent[T]
container, // document.getElementById("root")
transaction,
shouldReuseMarkup,
context
) {
...
var markup = ReactReconciler.mountComponent(
wrapperInstance,
transaction,
null,
ReactDOMContainerInfo(wrapperInstance, container),
context,
0 /* parentDebugID */
);
...
ReactMount._mountImageIntoNode(
markup,
container,
wrapperInstance,
shouldReuseMarkup,
transaction
);
}ReactReconciler.mountComponent 用于創(chuàng)建 DOM 元素，而 ReactMount._mountImageIntoNode 則是將剛創(chuàng)建的 DOM 元素掛載到頁面。ReactReconciler.mountComponent 會調(diào)用 ReactCompositeComponent[T]的 mountComponent 方法。在看 mountComponent 方法前，還需要先準備好 hostContainerInfo，由 ReactDOMContainerInfo 生成：
// 文件位置：src/renderers/shared/stack/reconciler/ReactContainerInfo.js
function ReactDOMContainerInfo(
topLevelWrapper, // ReactCompositeComponent[T]
node // document.getElementById("root")
) {
var info = {
_topLevelWrapper: topLevelWrapper,
_idCounter: 1,
_ownerDocument: node ?
node.nodeType === DOC_NODE_TYPE ? node : node.ownerDocument : null,
_node: node,
_tag: node ? node.nodeName.toLowerCase() : null,
_namespaceURI: node ? node.namespaceURI : null,
};
...
return info;
}現(xiàn)在各實例間的關(guān)系是這樣的：
再繼續(xù)看 mountComponent 方法：
// 文件位置：src/renderers/shared/stack/reconciler/ReactCompositeComponent.js
mountComponent: function (
transaction,
hostParent,
hostContainerInfo,
context
) {
...
// this._currentElement 為ReactElement[2](TopLevelWrapper)
var publicProps = this._currentElement.props;
var publicContext = this._processContext(context);
// TopLevelWrapper
var Component = this._currentElement.type;
...
// Initialize the public class
var doConstruct = shouldConstruct(Component);
// 生成TopLevelWrapper 實例
var inst = this._constructComponent(
doConstruct,
publicProps,
publicContext,
updateQueue
);
...
var markup;
...
markup = this.performInitialMount(renderedElement,
hostParent, hostContainerInfo, transaction, context
...
return markup;
},
performInitialMount: function (renderedElement, hostParent,
hostContainerInfo, transaction, context) {
// TopLevelWrapper 實例
var inst = this._instance;
...
// If not a stateless component, we now render
if (renderedElement === undefined) {
// 返回值為 ReactElement[1]
renderedElement = this._renderValidatedComponent();
}
// 返回 ReactNodeTypes.HOST
var nodeType = ReactNodeTypes.getType(renderedElement);
this._renderedNodeType = nodeType;
// instantiateReactComponent.js
var child = this._instantiateReactComponent(
renderedElement,
nodeType !== ReactNodeTypes.EMPTY /* shouldHaveDebugID */
);
this._renderedComponent = child;
var markup = ReactReconciler.mountComponent(
child,
transaction,
hostParent,
hostContainerInfo,
this._processChildContext(context),
debugID
);
...
return markup;
},當運行到var child = this._instantiateReactComponent時，就會調(diào)用上篇文章說到的instantiateReactComponent文件：
// 文件位置：src/renderers/shared/stack/reconciler/instantiateReactComponent.js
function instantiateReactComponent(node, shouldHaveDebugID) {
var instance;
...
} else if (typeof node === 'object') {
...
// element.type 為 ‘h2’
if (typeof element.type === 'string') {
instance = ReactHostComponent.createInternalComponent(element);
}
return instance;
}ReactDom 會在執(zhí)行的時候，執(zhí)行ReactDefaultInjection.inject()將 ReactDOMComponent 注入到 ReactHostComponent 中，ReactHostComponent.createInternalComponent 最終會調(diào)用 ReactDOMComponent：
// 文件位置：src/renderers/dom/shared/ReactDomComponent.js
function ReactDOMComponent(element) {
// h2
var tag = element.type;
validateDangerousTag(tag);
// ReactElement[1]
this._currentElement = element;
this._tag = tag.toLowerCase();
this._namespaceURI = null;
this._renderedChildren = null;
this._previousStyle = null;
this._previousStyleCopy = null;
this._hostNode = null;
this._hostParent = null;
this._rootNodeID = 0;
this._domID = 0;
this._hostContainerInfo = null;
this._wrapperState = null;
this._topLevelWrapper = null;
this._flags = 0;
}我們將返回的實例命名為 ReactDOMComponent[ins]。
ReactReconciler.mountComponent 會調(diào)用 ReactDomComponent 的 mountComponent 方法，這就會涉及到 HTML DOM 相關(guān)的內(nèi)容，我們在下一篇進行講解。
現(xiàn)在我們來看一下各實例間的關(guān)系：
目前為止的調(diào)用棧：
|=ReactMount.render(nextElement, container, callback) ___ |=ReactMount._renderSubtreeIntoContainer() | |-ReactMount._renderNewRootComponent() | |-instantiateReactComponent() | |~batchedMountComponentIntoNode() upper half |~mountComponentIntoNode() (平臺無關(guān)) |-ReactReconciler.mountComponent() | |-ReactCompositeComponent.mountComponent() | |-ReactCompositeComponent.performInitialMount() | |-instantiateReactComponent() _|_ |-ReactDOMComponent.mountComponent() lower half |-_mountImageIntoNode() (HTML DOM 相關(guān)下一篇講解) _|_
關(guān)于“React首次渲染中batchedMountComponentIntoNode做了什么”這篇文章就分享到這里了，希望以上內(nèi)容可以對大家有一定的幫助，使各位可以學(xué)到更多知識，如果覺得文章不錯，請把它分享出去讓更多的人看到。
