From 538421d67d76e2e48ee5fcadbb0369a19fe963cc Mon Sep 17 00:00:00 2001
From: zh-lx <18366276315@163.com>
Date: Mon, 8 Nov 2021 23:21:18 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BA=94:=203.diff=20=E5=B9=B6=E6=B7=BB?=
 =?UTF-8?q?=E5=8A=A0=20flag?=
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---
 src/mini-react/reconciler.js | 60 ++++++++++++++++++++++++++++++------
 1 file changed, 50 insertions(+), 10 deletions(-)

diff --git a/src/mini-react/reconciler.js b/src/mini-react/reconciler.js
index bf96d7c..073b67d 100644
--- a/src/mini-react/reconciler.js
+++ b/src/mini-react/reconciler.js
@@ -1,24 +1,64 @@
 export function reconcileChildren(workInProgress, elements) {
   let index = 0; // 当前遍历的子元素在父节点下的下标
   let prevSibling = null; // 记录上一个兄弟节点
+  let oldFiber = workInProgress?.alternate?.child; // 对应的旧 fiber
 
-  while (index < elements.length) {
-    // 遍历子元素
+  while (index < elements.length || oldFiber) {
+    // 遍历 elements 和 oldFiber
     const element = elements[index];
     // 创建新的 fiber
-    const newFiber = {
-      element,
-      return: workInProgress,
-      stateNode: null,
-    };
+    let newFiber = null;
+    const isSameType =
+      element?.type &&
+      oldFiber?.element?.type &&
+      element.type === oldFiber.element.type;
+
+    // 添加 flag 副作用
+    if (isSameType) {
+      // type相同，表示更新
+      newFiber = {
+        element: {
+          ...element,
+          props: element.props,
+        },
+        stateNode: oldFiber.stateNode,
+        return: workInProgress,
+        alternate: oldFiber,
+        flag: 'Update',
+      };
+    } else {
+      // type 不同，表示添加或者删除
+      if (element || element === 0) {
+        // element 存在，表示添加
+        newFiber = {
+          element,
+          stateNode: null,
+          return: workInProgress,
+          alternate: null,
+          flag: 'Placement',
+          index,
+        };
+      }
+      if (oldFiber) {
+        // oldFiber存在，删除 oldFiber
+        oldFiber.flag = 'Deletion';
+      }
+    }
+
+    if (oldFiber) {
+      // oldFiber 存在，则继续遍历其 sibling
+      oldFiber = oldFiber.sibling;
+    }
+
     if (index === 0) {
       // 如果下标为 0，则将当前fiber设置为父 fiber 的 child
       workInProgress.child = newFiber;
-    } else {
-      // 否则通过 sibling 作为兄弟 fiber 连接
+      prevSibling = newFiber;
+    } else if (newFiber) {
+      // newFiber 和 prevSibling 存在，通过 sibling 作为兄弟 fiber 连接
       prevSibling.sibling = newFiber;
+      prevSibling = newFiber;
     }
-    prevSibling = newFiber;
     index++;
   }
 }