题：
如何使用javascript(和node.js)在Firebase中实现高效的无限滚动？
我检查了什么：
Implementing Infinite Scrolling with Firebase?
问题：老火山^
Infinite scroll with AngularJs and Firebase
代码来自：
Infinite scroll with AngularJs and Firebase
“首先,我建议在你的Firebase中创建一个索引.对于这个答案,我创建了这个：
{
"rules": {
".read": true,".write": false,"messages": {
".indexOn": "id"
}
}
}
然后,让我们用Firebase做一些魔术：
// @fb: your Firebase.
// @data: messages,users,products... the dataset you want to do something with.
// @_start: min ID where you want to start fetching your data.
// @_end: max ID where you want to start fetching your data.
// @_n: Step size. In other words,how much data you want to fetch from Firebase.
var fb = new Firebase('https://最后,更好的无限滚动(没有jQuery)：
window.addEventListener('scroll',function() {
if (window.scrollY === document.body.scrollHeight - window.innerHeight) {
getDataset();
}
});
我正在使用React这种方法,无论你的数据有多大,它的速度都很快.“
(回答于2015年10月26日15:02)
(作者：Jobsamuel)
问题
在该解决方案中,每当滚动到达屏幕高度的末尾时,将加载n个帖子.
根据屏幕尺寸的不同,这意味着在某些时候会加载比所需更多的帖子(屏幕高度仅包含2个帖子,这意味着每当我们到达屏幕高度结束时,将会加载3个以上的帖子.例如= 5).
这意味着每次我们到达滚动高度结束时,将加载3 * NumberOfTimesScrollHeightHasBeenPassed比所需更多的帖子.
MY CURRENT CODE(一次加载所有帖子,无限滚动)：
var express = require("express");
var router = express.Router();
var firebase = require("firebase");
router.get('/index',function(req,res,next) {
var pageRef = firebase.database().ref("posts/page");
pageRef.once('value',function(snapshot){
var page = [];
global.page_name = "page";
snapshot.forEach(function(childSnapshot){
var key = childSnapshot.key;
var childData = childSnapshot.val();
page.push({
id: key,title: childData.title,image: childData.image
});
});
res.render('page/index',{page: page});
});
});
最佳答案
这是无限分页的完整代码.
createPromiseCallback函数用于支持promise和callback.
function createPromiseCallback() {
var cb;
var promise = new Promise(function (resolve,reject) {
cb = function (err,data) {
if (err) return reject(err);
return resolve(data);
};
});
cb.promise = promise;
return cb;
}
function getPaginatedFeed(endpoint,pageSize,earliestEntryId,cb) {
cb = cb || createPromiseCallback();
var ref = database.ref(endpoint);
if (earliestEntryId) {
ref = ref.orderByKey().endAt(earliestEntryId);
}
ref.limitToLast(pageSize + 1).once('value').then(data => {
var entries = data.val() || {};
var nextPage = null;
const entryIds = Object.keys(entries);
if (entryIds.length > pageSize) {
delete entries[entryIds[0]];
const nextPageStartingId = entryIds.shift();
nextPage = function (cb) {
return getPaginatedFeed(endpoint,nextPageStartingId,cb);
};
}
var res = { entries: entries,nextPage: nextPage };
cb(null,res);
});
return cb.promise;
}
var endpoint = '/posts';
var pageSize = 2;
var nextPage = null;
var dataChunk = null;
getPaginatedFeed(endpoint,pageSize).then(function (data) {
dataChunk = data.entries;
nextPage = data.nextPage;
//if nexPage is null means there are no more pages left
if (!nextPage) return;
//Getting second page
nextPage().then(function (secondpageData) {
dataChunk = data.entries;
nextPage = data.nextPage;
//Getting third page
if (!nextPage) return;
nextPage().then(function (secondpageData) {
dataChunk = data.entries;
nextPage = data.nextPage;
//You can call as long as your nextPage is not null,which means as long as you have data left
});
});
});
怎么样的问题放在屏幕上有多少项,你可以给出这样的解决方案,每个帖子给出固定的x高度,如果需要更多的空间,在帖子底部放置“阅读更多”链接,这将显示缺失用户点击时的一部分.在这种情况下,您可以在屏幕上保留固定的项目数.此外,您可以检查屏幕分辨率,以便放置更多或更少的项目.
