本地数据库和server端数据库比对思路

async function fetchServerDataPage(startId, endId, pageSize) {
    // 获取 id 大于 startId 的数据 小于endId
  return await fetch(`/server-data?startId=${startId}&endId=${endId}&size=${pageSize}`).then(res => res.json());
}

async function fetchLocalDataPage(startId, endId, pageSize) {
    // 获取 id 大于 startId 的数据 小于endId
  return await fetch(`/local-data?startId=${startId}&endId=${endId}&size=${pageSize}`).then(res => res.json());
}

function diffPage(serverData, localData) {
    const patches = [];
    const serverMap = new Map();
    serverData.forEach(item => serverMap.set(item.id, item));

    localData.forEach(localItem => {
        const serverItem = serverMap.get(localItem.id);
        if (!serverItem) {
            patches.push({type: 'remove', id: localItem.id});
        } else if (serverItem.value !== localItem.value) {
            patches.push({type: 'update', id: localItem.id, newValue: serverItem.value});
        }
        serverMap.delete(localItem.id);
    });

    serverMap.forEach((serverItem, id) => {
        patches.push({type: 'add', id, value: serverItem.value});
    });

    return patches;
}

async function diffAllData(pageSize) {
    let startId = 0;
    let endId = 50;
    let serverData, localData;
    let allPatches = [];

    while (true) {
        // 获取下一页数据
  [serverData, localData] = await Promise.all([fetchServerDataPage(startId, endId, pageSize), fetchLocalDataPage(startId, endId, pageSize)]);

        // 如果两边都没有数据了，终止循环
  if (serverData.length === 0 && localData.length === 0) {
            break;
        }

        // 比对当前页的数据
  const patches = diffPage(serverData, localData);
        allPatches = allPatches.concat(patches);

        if (serverData.length > 0 || localData.length > 0) {
            startId = endId;
            endId += 50;
        }
    }

    return allPatches;
}

// 调用 diffAllData 函数进行比对处理
const pageSize = 100; // 每页的数据量
diffAllData(pageSize).then(allPatches => {
    console.log(allPatches);
});

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