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JSON Object (how to not load the entire object on DOM initially)

So i am reading a local json file that consist of {[Object,Object,Object.....]}
I am using the
$.getJSON('products.json', function (pdata) {
for (var i = 0; i < pdata.data.length; i++) {
AppendtoDom(pdata.data[i]);
}
The above code reads the json objects and appends to the DOM, but i want to initially load only 100 objects at a time and on scroll keep appending.
Say there are around 1200 objects. How do i go about this?
My implementaion so far
$(function(){
loadData();
});
function loadData(){
$.getJSON('products.json', function (pdata) {
var i = 0;
function addtoDom(num){
var limit = Math.min(i + num, pdata.data.length);
for(; i < limit; i++){
getInformation(pdata.data[i]);
}
}
addtoDom(100);
$('.content').jscroll({
callback: addtoDom(100)
});
});
}
function getInformation(obj){
var content = "";
for (var i = 0; i < 4; i++) {
content += '<li>';
content += "<img src='" + obj.imageUrl + "' style='width:200px;height:200px'/>";
content += '<div class="productName">' + obj.fullName + "</div>";
content += '<div class="price">Price: ' + obj.price + "</div>";
content += '</li>';
}
$("<ul class= 'view'>" + content + "</ul>").appendTo('.content');
}
Similar question i asked in How would i implement an infinite scroll in my DOM

You can put all the objects you get back from the Ajax call into a persistent variable, add the first 100 to the DOM, keep a counter of how many you've added so far and then upon scrolling to a certain point, add another 100, add another 100 and so on.
$.getJSON('products.json', function (pdata) {
var i = 0;
function addMore(num) {
var limit = Math.min(i + num, pdata.data.length);
for (; i < limit; i++) {
AppendtoDom(pdata.data[i]);
}
}
// add the first 100
addMore(100);
// then set up whatever scroll detection you want here and
// when you decide that it has scrolled enough to add some more
// you just call addMore(100) again
});
In your specific implementation of the above idea, you have an implementation mistake. You have to pass a function reference for the callback so change this:
$('.content').jscroll({
callback: addtoDom(100)
});
to this:
$('.content').jscroll({
callback: function() {addtoDom(100);}
});

Assign your JSON to a variable and dynamically render them as needed.
var json;
$.getJSON('products.json', function (pdata) {
JSON = pdata;
};
// Scheduling logic
AppendtoDom(json[i]);

Asynchronous Problems with Javascript Hacker News API

Hacker News recently released an API that I am using to display what the current top ten items are on Hacker News. I am running into some problems.
When I run the code below, the order of the items on the frontpage are inaccurate, jumping from the second one in the frontpage to the fourth, to the first, to the fifth, to the third and so on. Running the code again results in a slightly different order again.
$.getJSON('https://hacker-news.firebaseio.com/v0/topstories.json', function(json) {
var convoText = '<ol>';
for (var i = 0; i < 10; i++) {
(function(i) {
$.getJSON('https://hacker-news.firebaseio.com/v0/item/' + json[i] + '.json', function(json2) {
convoText += '<li>' + json2.title + '</li>';
if (i === 9) {
convoText += '</ol>';
addConvo(convoText);
}
});
})(i);
}
});
I understand that this is an effect of Javascript's asynchronous nature. How can I fix it?

The knack is to create and append a <li><a></a></li> structure synchronously in the loop - thereby establishing the correct order - then populate it asynchronously with json2 data when it arrives.
$.getJSON('https://hacker-news.firebaseio.com/v0/topstories.json', function(json) {
var $ol = $('<ol/>').appendTo(...);//wherever
for (var i = 0; i < Math.min(json.length, 10); i++) {
(function(i) {
var $a = $('<li><a></a></li>').appendTo($ol).find('a');
$.getJSON('https://hacker-news.firebaseio.com/v0/item/' + json[i] + '.json', function(json2) {
$a.attr('href', json2.url).text(json2.title);
});
})(i);
}
});
You will have to complete the .appendTo(...) line. I don't know from the question where the <ol>...</ol> is appended.

You can use jQueries $.when for that:
$.getJSON('https://hacker-news.firebaseio.com/v0/topstories.json', function(json) {
var requests = [];
for (var i = 0; i < 10; i++) {
requests.push($.getJSON('https://hacker-news.firebaseio.com/v0/item/' + json[i] + '.json'));
}
$.when.apply($, requests).done(function() {
var results = [].slice.call(arguments);
var list = results.map(function(arr) {
return '<li>' + arr[0].title + '</li>';
});
var convoText = '<ol>' + list.join('') + '</ol>';
console.log(convoText);
});
});

There are a few ways to fix this. The easiest is, instead of appending to convoText, use an array, and set its index when you get data. Like data[i] = json2;. Then when all your data is fetched, join your array.
A more structural fix would be to rearchitect your loop as a collection of promises, and construct your HTML when they have all resolved (what #xat was alluding to above).

How to prevent a ajax function in javascript to be executed several times at once

I am building search engine with PLAY Framework 2.2.1 and have problems with listing the results. The search results are stored in the cache provided by the framework and can be accessed with the uniqe id. I don't want the results to get displayed all at once, so the result list is fetched in chunks via ajax.
The first part after the result site has loaded and the rest every time when a certain scroll event occurs.
Now the problem is that some of the results are listed several times and the alert messages
tell me that the function next_results sometimes gets executed with the same value for variable pos twice or more times.
To prevent this issue I use the processing variable but this doesn't seem to work properly.
var processing = false;
var not_finished = true;
var pos = 0;
function next_results(uuid, result_size){
alert("input\n" + result_size + " result_size\ncurrent_position" + pos);
jsRoutes.controllers.Application.getResults(uuid, pos, result_size).ajax({
success : function(data) {
var len = data.length;
// alert("input\n" + result_size + " result_size\ncurrent_position" + pos + "\n result_length" + len);
pos = pos + len;
if (len == 0){
not_finished = false;
} else {
for (var i = 0; i < len; i++) {
var result= data[i];
$('#results').append(result.string);
};
}
}
});
}
var uuid;
function set_uuid (x){
uuid = x;
}
$(document).ready(function(){
//initial
if (!processing){
processing = true;
next_results(uuid, 10);
processing = false;
}
$(document).scroll(function(e){
if (processing)
return false;
if (not_finished && $(window).scrollTop() >= $(document).height() - $(window).height() - 300){
processing = true;
next_results(uuid, 2);
processing = false;
}
});
});
The unique id is set in the html code (via Scala):
<script>set_uuid('#uuid');</script>

next_results(uuid, 2);
processing = false; <-- WRONG
You need to do it in the success function
success : function(data) {
...
...
processing = false;
}

Nested asynchronous calls do not seem to execute as expected

While trying out jQuery, I have a question that is probably a newbie mistake, but I cannot seem to find the solution. This is the code:
$.get("index.html", function() {
var i = 0;
for (; i < 3; i++)
{
var lDiv = document.createElement('div');
lDiv.id = 'body-' + i;
document.getElementById('body').appendChild(lDiv);
$.get('index.html', function(data) {
lDiv.innerHTML = "<p>Hello World " + i + "</p>";
});
}
});
The output seems to be
<div id='body-0'></div>
<div id='body-1'></div>
<div id='body-2'>
<p>Hello World 3</p>
</div>
I expected the lDiv.innerHTML= code to be executed for each i, but apparently it is only executed for the last i? What am I overlooking?

This happens because the loop completes (i is 2) before any of the callbacks are fired.
#thecodeparadox's solution works, but it serializes the HTTP requests. (Makes them fire one-at-a-time.) This allows the requests to execute in parallel, and thus quicker:
for (var i = 0; i < 3; i++)
{
var lDiv = document.createElement('div');
lDiv.id = 'body-' + i;
document.getElementById('body').appendChild(lDiv);
$.get('index.html', function(i,lDiv) { // the current iteration's `i` and `lDiv` are captured...
return function(data) {
lDiv.innerHTML = "<p>Hello World " + i + "</p>";
}
}(i,lDiv)); // ...by passing them as an argument to the self-executing function
}

As $.get() is asynchronous, so you need to execute your append and next call within $.get()'s success() callback function.
var i = 0;
function recursiveLoad() {
if(i == 3) return;
var lDiv = document.createElement('div');
lDiv.id = 'body-' + i;
document.getElementById('body').appendChild(lDiv);
$.get('index.html', function(data) {
lDiv.innerHTML = "<p>Hello World " + i + "</p>";
i++;
recursiveLoad();
});
}
// initial call
recursiveLoad();

Jquery Ajax image load works only in FF. Suspect "race condition."

I made a web app that loads images using jquery, ajax and json. I got it to work in Firefox, but alas, Safari and Chrome remain stubborn.
It has to do with a "race condition" where images don't load quickly enough, so I have a load event as well as a trigger event to wait until all images are loaded before appending the html to a container div.
Here is the link to the page that works in FF:
http://chereecheree.com/dagworthy/style.html
And some code:
var aSectionImages = new Array;
//count how many images are in a section:
var aImagesCount = new Array();
//count how many images of a particular section have been loaded
var aImagesLoaded = new Array();
var htmlString;
var jsonStyleImages = "images.json"
var jsonNavImages = "imagesNav.json";
//container div:
var scrollableArea = $("#scrollableArea");
$.getJSON(jsonNavImages, getNavIcons);
$.getJSON(jsonStyleImages, makeScroller);
//trigger this function on load event:
function imageLoaded(oImg){
//get the name of the section of images:
var locSectionId = (imageInSection(oImg.src)).replace(/\s|'/g, "_");
//get the file name of the current image
var locFileName = getFileName(oImg.src);
if (aImagesLoaded[locSectionId]===undefined){
aImagesLoaded[locSectionId] = new Array;
};
//check if it has already been loaded by seeing if it exists in the array of loaded images:
var inArray = false;
inArray = $.inArray(locFileName, aImagesLoaded[locSectionId]);
if (inArray == -1) {
//array.push returns the new length of the array:
var tempLength = aImagesLoaded[locSectionId].push(locFileName);
}
if (tempLength==aImagesCount[locSectionId]){
htmlString += "</div>";
scrollableArea.append(htmlString);
//after the html has been appended, force it to be 1000 px -- totally unstable hack.
scrollableArea.width(1000);
}
}
//helper function to get section name of a loading image:
function imageInSection(src){
var resultId=false;
var locFileName = getFileName(src);
for (var k = 0; k < aSectionImages.length; k++){
for(var j=0; j < aSectionImages[k].images.length; j++){
tempSrc = aSectionImages[k].images[j].src.split("/");
tempFileName = tempSrc[tempSrc.length-1];
if (tempFileName == locFileName) {
resultId = aSectionImages[k].id;
}
}
}
return resultId;
}
//helper function to get the file name of a loading image:
function getFileName(href){
var resultFileName=false;
var locSrc = href.split("/");
resultFileName = (locSrc[locSrc.length-1]);
return resultFileName;
}
//function called when ajax request is successful -- it puts together the html string that will be appended to the containter div
function makeScroller(data){
aSectionImages = data;
for (ii=0; ii<aSectionImages.length; ii++){
var locData = aSectionImages[ii];
var locId = locData.id.replace(/\s|'/g, "_");
aImagesCount[locId] = locData.images.length;
htmlString = "<div id=\"" + locId + "\">";
for (jj=0; jj<locData.images.length; jj++){
var oImage = new Image();
var locImage = locData.images[jj];
$(oImage)
.load(function(){
imageLoaded(oImage);
})
.attr("src", locData.images[jj].src);
if (oImage.complete && oImage.naturalWidth !== 0){
$(oImage).trigger("load");
}
//alert (oImage.width);
locImage.id ? locImage.id = " id=\""+locImage.id+"\" " : locImage.id = "";
htmlString += "<img height=\"" + locImage.height + "\"" + " width=\"" + oImage.width + "\"" + locImage.id + " src=\"" + locImage.src + "\" />";
}
}
}
But it's probably best to look at it online, as there is a plugin that's used.
Anyhow, the computed style for the container div shows up at "0px" sometimes, which is why I'm forcing it to "1000px" but that hack is not very stable.
Any ideas would be greatly appreciated.
Thanks!
--Daniel.

In this section:
$(oImage)
.load(function(){
imageLoaded(oImage);
})
.attr("src", locData.images[jj].src);
if (oImage.complete && oImage.naturalWidth !== 0){
$(oImage).trigger("load");
}
image.naturalWidth isn't available in all browsers (so undefined !== 0 won't be a correct check), but you don't need it to use it, just rearrange the code, like this:
$(oImage).one('load', function(){ imageLoaded(this); })
.attr("src", locData.images[jj].src)
.each(function() {
if (this.complete) $(this).trigger("load");
});
This uses .each() to loop through after setting the src and triggers the load event in case it came from cache (this.complete being instantly true indicates this). The .one() call ensures the load event only fires once, whether from cache or a normal load.