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Asked: 2026-06-04T08:06:56+00:00

I’m building a guestlist app for my company using PHP, Javascript/jQuery/Ajax, JSON and localstorage.

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I’m building a guestlist app for my company using PHP, Javascript/jQuery/Ajax, JSON and localstorage. It will be used on smartphones: primarily Iphone 4. I’m using localstorage as my cache since the search-part of the application has to work in offline mode.

I’m having performance issues while searching through a guestlist.

The app’s flow looks like this (for this examaple I’m working with guestlist which contains 600 guests)

1. Retrieve all guests from the server with PHP encode with JSON and send back to js via AJAX. This works fine.

2. Parse the PHP responseText (called phpData) using JSON.Parse: 

var parsedMysqlData = JSON.parse(phpData);

which gives us an JSON.Array containing 600 objects looking like this:

Object:  {
Id: Int
EventId: int
guestInfo: string
guestlist: string
guestName: string
reference: string
total: int
used: int
}

3. Save the JSON.Array to the user’s localstorage using JSON.Stringify:

 localStorage.setItem(0, JSON.stringify(parsedMysqlData));

4. when the user starts searching we get his search string then retrieve our guestlist using JSON.parse in localstorage like this:

 var currentGuestlist = JSON.parse(localStorage.getItem(0));

And then iterate through our objects using this for-loop trying to match his search string with our guests the array currentGuestlist:

 for (i=0; i<currentGuestlist.length; i++) {
 // match 'currentGuestList[i]['name']' with what the user typed in search form 
}

For some reason this takes a really long time on an iPhone 4. Searching through 600 objects will freezes the iphone for about 4 seconds before returning the matches.

Before storing arrays containing JSON objects in localStorage and parsing it with JSON, I simply stored unordered strings in localStorage and it work a whole lot faster. The JSON objects ad structure to the data stored in localStorage which is crucial. So I guess the speed issue has to have something to do with the fact that I’m using JSON objects? How can i structure my data i localStorage in an organized way while still maintaining as good speed performance as before?

Lastly anykind of tips or advice on which techniques you would use to make this app as lightweight and fast as possible is greatly appreciated.

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1 Answer

  1. Editorial Team

    Are you fetching the list per each search from the local storage? Don’t do that, instead store it in the local storage only as needed (whenever it changes), and keep it always as a data structure.

    Simply having objects instead of plain strings cannot be the reason for slowness, as everything in JavaScript is an object already, and thus it should only be slowing by a constant factor.

    Furthermore, if this is about autocomplete kind of behaviour, then I suggest you would slow down the search, and also consider that if the user types in the box “Ma”, the list gets filtered, and the user adds “tt” for “Matt”, only previously filtered matches need to be considered…

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