Develop Reference

React JS - Best way to have coninues results for every key stroke using a REST calls to server?

In short we have a massive database and need to provide results as the user types them in the search box. It is impossible for us to preload queries and attempt to match that way.
Currently we send a request to the server with the new query string every 2 chars or 5 seconds. This is a bit of a mess however, so I'm looking to see if there is a faster/better way of doing this.
Previous solutions I've seen would require pre-feteching which in our case is not possible and considering the size of the return too costly.

I would recommend using debounce for this. It will make the function wait a certain amount of time after being called before running. Additional calls to the function will reset the timer. That way, the function will not run until users have finished (or paused) typing.
This which will prevent unnecessary load on your database, while still providing a good user experience (as long as you have a reasonable debounce time). Examples of how to do debounce in React can be found here

Best Server API and Client Side Javascript Interaction Methods?

Currently, I'm using setTimeout() to pause a for loop on a huge list so that I can add some styling to the page. For instance,
Eg: http://imdbnator.com/process?id=wtf&redirect=false
What I use setTimeOut for:
I use setTimeout() to add images,text and css progress bar (Why doesn't Progress Bar dynamically change unlike Text?2).
Clearly, as you can see it is quite painful for a user to just browse through the page and hover over a few images. It gets extremely laggy. Is there any any workaround to this?
My FOR Loop:
Each for loop makes an ajax request on the background to a PHP API. It definitely costs me some efficiency there but how do all other websites pull it off with such elegance? I mean, I've seen websites show a nice loading image with no user interference while it makes an API request. While I try to do something like that, I have set a time-out everytime.
Is that they use better Server-Client side interaction languages like the node.js that I've heard?
Also, I'e thought of a few alternatives but run into other complications. I would greatly appreciate if you can help me on each of these possible alternatives.
Method 1:
Instead of making an AJAX call to my PHP API through jQuery, I could do a complete server side script altogether. But then, the problem I run into is that I cannot make a good Client Side Page (as in my current page) which updates the progress bar and adds dynamic images after each of the item of the list is processed. Or is this possible?
Method 2: (Edited)
Like one the useful answers below, I think the biggest problem is the server API and client interaction. Websockets as suggested by him look promising to me. Will they necessarily be a better fix over a setTimeout? Is there any significant time difference in lets say I replace my current 1000 AJAX requests into a websocket?
Also, I would appreciate if there is anything other than websocket that is better off than an AJAX call.
How do professional websites get around with a fluidic server and client side interactions?
Edit 1: Please explain how professional websites (such as http://www.cleartrip.com when you are requesting for flight details) provide a smooth client side while processing the server side.
Edit 2: As #Syd suggested. That is something that I'm looking for.I think there is a lot of delay in my current client and server interaction. Websockets seem to be a fix for that. What are the other/ best ways for improving server cleint interaction apart from the standard AJAX?

Your first link doesn't work for me but I'll try to explain a couple of things that might help you if I understand your overall problem.
First of all it is bad to have synchronous calls with large amount of data that require processing in your main ui thread because the user experience might suffer a lot. For reference you might want to take a look into "Is it feasible to do an AJAX request from a Web Worker?"
If I understand correctly you want to load some data on demand based on an event.
Here you might want to sit back and think what is the best event for your need, it's quite different to make an ajax request every once in a while especially when you have a lot of traffic. Also you might want to check if your previous request has completed before you initialize the next one (this might not be needed in some cases though). Have a look at async.js if you want to create chained asynchronous code execution without facing the javascript "pyramid of doom" effect and messy code.
Moreover you might want to "validate - halt" the event before making the actual request. For example let's assume a user triggers a "mouseenter" you should not just fire an ajax call. Hold your breath use setTimeout and check if the user didn't fire any other "mouseenter" event for the next 250 ms this will allow your server to breath. Or in implementations that load content based on scroll. You should not fire an event if the user scrolls like a maniac. So validate the events.
Also loops and iterations, we all know that if the damn loop is too long and does heavy lifting you might experience unwanted results. So in order to overcome this you might want to look into timed loops (take a look at the snippet bellow). basically loops that break after x amount of time and continue after a while. Here are some references that helped me with a three.js project. "optimizing-three-dot-js-performance-simulating-tens-of-thousands-of-independent-moving-objects" and "Timed array processing in JavaScript"
//Copyright 2009 Nicholas C. Zakas. All rights reserved.
//MIT Licensed
function timedChunk(items, process, context, callback){
var todo = items.concat(); //create a clone of the original
setTimeout(function(){
var start = +new Date();
do {
process.call(context, todo.shift());
} while (todo.length > 0 && (+new Date() - start < 50));
if (todo.length > 0){
setTimeout(arguments.callee, 25);
} else {
callback(items);
}
}, 25);
}
cleartip.com will probably might use some of these techniques and from what I've seen what it does is get a chunk of data when you visit the page and then upon scroll it fetches other chunks as well. The trick here is to fire the request a little sooner before the user reaches the bottom of the page in order to provide a smooth experience. Regarding the left side filters they only filter out data that are already in the browser, no more requests are being made. So you fetch and you keep something like cache (in other scenarios though caching might be unwanted for live data feeds etc).
Finally If you are interested for further reading and smaller overhead in data transactions you might want to take a look into "WebSockets".

You must use async AJAX calls. Right now, the user interaction is blocked while the HTTP ajax request is being done.
Q: "how professional websites (such as cleartrip.com) provide a smooth client side while processing the server side."
A: By using async AJAX calls

Avoiding content reload without use of frames/iframes

There are plenty of reasons to want to avoid <iframe>s (and indeed frames in general) but what are the best alternatives? (The intent here being to avoid full page reloads).
Facebook, for instance, seems to keep its top bar and side menu in tact (for the most part) and a full page reload incredibly rare.
Searching for explanations with little idea of what to use as search terms has rendered me little insight, so I thought it best to raise the question here. Is this all Ajax, or is there more to it than that?

AJAX
The more traditional approach is "AJAX". In a nutshell, your javascript code can request specific content from the server on a time (every x seconds) or when a user event happens (e.g. a button click).
A very basic implementation in jQuery would look something like:
function updateShouts(){
// Assuming we have #shoutbox
$('#shoutbox').load('latestShouts.php');
}
setInterval( "updateShouts()", 10000 );
This will update a div with id "shoutbox" every 10 seconds with whatever content is retrieved from latestShouts.php.
More advanced implementation would involve retrieving only data (not presentation) in a format like JSON or XML, and then updating the existing HTML values with the data that was received.
WebSockets
More recently, browsers have started supporting something called WebSockets. WebSockets allow you to keep a bidirectional connection open between the browser and the server, and it allows the server to push information to the browser without the browser requesting it.
This is more efficient in many ways; with the main reason being the fact that you don't have to waste server calls every x seconds to check if data is there. WebSockets allow you to display information from the server almost as soon as it becomes available.
I hope that helps..
Cheers!

Injecting partial content using ajax is your best and easiest bet - I recommend jquery too.

Ways to make Javascript code hacking / injection / manipulation difficult?

Are there ways to prevent, or make it difficult enough, for someone to inject Javascript and manipulate the variables or access functions? A thought I had is to change all var names randomly on each reload so the malware script would need to be rewritten every time? Or are there other less painful ways?
I understand that eventually someone will hack his way in, but I'd like to know ways to make it difficult to reproduce the action, so that people won't publish a bookmarklet or something similar for everyone to use. I don't care if experts find their way in the code, but I'd like it to be a bit more complex than javascript:d=0;
If you know ways to make hacking Javascript a bit more difficult, please write those.

Accept that your javascript will be "manipulated" and make provision at the server side. There's fundamentally nothing you can do to stop people tinkering with the client.

You can write your JS to use only private methods and variables in a self-executing function. For example, the following code leaves no sign of itself in the global namespace for anyone to monkey with.
(function(){
var x = 1;
var y = 2;
var z = "A am z";
var clickHandler = function() {
alert('You clicked the body');
};
document.getElementsByTagName('body')[0].addEventListener('click',clickHandler,true);
}());
[EDIT]
The above code is susceptible to a user overwriting any globally available objects, methods, events or properties you are using (in this case, document, getElementsByTagName and addEventListener), so if you are truly paranoid you can copy these to your function scope before the page has loaded and the user has a chance to overwrite them. Using addEventListener is a good idea because unlike the event body.onclick, it cannot be removed or overwritten from outside the function.

Any user that will really want to tamper with the client will be able to. The code is on his machine. Even if you obfuscate the client side code, there are tools out their that will help someone deobfuscate the code back in a second.
What you need to think about though is making the site safe on the server, and safe for other users as well.
This means (as a minimum):
Checking/Validating every request and input parameters on the server so Users won't be able to alter any server side data by triggering 'hacked' client side functions you wrote.
Check all data that you output to the screen that was originated from user input. Other users might have inserted client side scripts that are dangerous for your site, and especially dangerous to the other users on your site. (If you're using .net then check out the AntiXSS library)

Obfuscation and minification should make it a good bit more difficult to hack, but I agree with spender.

how to increase Speed of a component made from Javascript or JQuery?

I want to make my component faster, I am using Javascript and JQuery to build that.
I am using JSON object to communicate with component and back-end is python.
Is there any suggestion to make component faster?

Setup some analysis to see what takes time to process. Then decide if you want to try to optimize the javascript and client code, the communication up/down with the server or the actual speed of the python execution. When you have decided what you want to make faster, you can post samples of that to this site and people will probably be willing to help you.

On the client side, you can benchmark your script(s) using getTime()
var start = (new Date).getTime();
/* Run your script. */
var diff = (new Date).getTime() - start;
alert(diff)
And see what is taking long in a script exactly.
But its hard do tell what could be optimized if you don't post any code.

If speed is the issue, and you by profiling discover that js is the culprit, then I would look into replacing the jQuery with vanilla javascript, or a more optimized library.
As jQuery tries to do 'everything' and trains its users into wrapping everything in $(), its bound to introduce unnecessary method calls (I've seen that a single call to $() can result in upto 100+ method calls).