Preloading images with jQuery

Question

I m looking for a quick and easy way to preload images with JavaScript  I m using jQuery if that s important   I saw this here  http   nettuts com       function complexLoad config  fileNames      for  var x   0  x  lt  fileNames length  x              lt img gt    attr         id  fileNames x         src  config imgDir   fileNames x    config imgFormat        title   The     fileNames x      nebula         appendTo       config imgContainer  css   display   none               But  it looks a bit over-the-top for what I want   I know there are jQuery plugins out there that do this but they all seem a bit big  in size   I just need a quick  easy and short way of preloading images

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jQuery preloadImage function src onSuccess onError                var img   new Image           img src src          var error false          img onerror function                error true              if onError onError call img                     if error  false              setTimeout function                if img height gt 0 amp  amp img width gt 0                    if onSuccess onSuccess call img                   return img                  else                   setTimeout arguments callee 5                              0           return img              jQuery preloadImages function arrayOfImages           jQuery each arrayOfImages function                jQuery preloadImage this                        example        jQuery preloadImage           img someimage jpg           function                  complete             this width  0    true                                   function                  error

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I have a small plugin that handles this   It s called waitForImages and it can handle img elements or any element with a reference to an image in the CSS  e g  div   background  url img png      If you simply wanted to load all images  including ones referenced in the CSS  here is how you would do it        body   waitForImages       waitForAll  true      finished  function               All images have loaded

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this jquery imageLoader plugin is just 1 39kb  usage         imageLoader       images   src1 src2 src3          allcomplete function e ui             images are ready here           your code - site fadeIn   or something like that             there are also other options like whether you want to load the images synchronously or asychronously and a complete event for each individual image

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This one line jQuery code creates  and loads  a DOM element img without showing it       lt img src  img 1 jpg   gt

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For those who know a little bit of actionscript  you can check for flash player  with minimal effort  and make a flash preloader  that you can also export to html5 Javascript Jquery  To use if the flash player is not detected  check examples on how to do this with the youtube role back to html5 player   And create your own  I do not have the details  becouse i have not started yet  if i dont forgot  i wil post it later and will try out some standerd Jquery code to mine

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This works for me even in IE9       lt img src      imgURL       gt    on  load   function    doOnLoadStuff

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I usually use this snippet of code on my projects for the loading of the images in a page  You can see the result here https   jsfiddle net ftor34ey    lt script src  https   ajax googleapis com ajax libs jquery 3 5 1 jquery min js  gt  lt  script gt    lt img src  https   live staticflickr com 65535 50020763321 d61d49e505 k d jpg  width  100    gt   lt img src  https   live staticflickr com 65535 50021019427 692a8167e9 k d jpg  width  100    gt   lt img src  https   live staticflickr com 65535 50020228418 d730efe386 k d jpg  width  100    gt   lt img src  https   live staticflickr com 65535 50020230828 7ef175d07c k d jpg  width  100    gt    lt div style  background-image  url https   live staticflickr com 65535 50020765826 e8da0aacca k d jpg    gt  lt  div gt   lt style gt       bg           background-image  url  https   live staticflickr com 65535 50020765651 af0962c22e k d jpg           lt  style gt   lt div class  bg  gt  lt  div gt    lt div id  loadingProgress  gt  lt  div gt    The script save in an array all the src and background-image of the page and load all of them   You can see read show the progress of the loading by the var loadCount   let backgroundImageArray        function backgroundLoading i         let loadCount   0       let img   new Image          img  on  load   function               if  i  lt  backgroundImageArray length                 loadCount   parseInt   100   backgroundImageArray length    i                backgroundLoading i   1              else                loadCount   100                 do something when the page finished to load all the images             console log  loading completed                       loadingProgress   append   lt div gt loading completed    lt  div gt                         console log loadCount                     loadingProgress   append   lt div gt     loadCount      lt  div gt             attr  src   backgroundImageArray i - 1          document  ready function                  each function               var backgroundImage     this  css  background-image            var putInArray   false           var check   backgroundImage substr 0  3            if  check     url                  backgroundImage   backgroundImage split  url    join     split      join                  backgroundImage   backgroundImage replace                       backgroundImage   backgroundImage replace                        if  backgroundImage substr 0  4      http                     backgroundImage   backgroundImage                            putInArray   true             else if    this  get 0  tagName     IMG                  backgroundImage     this  attr  src                putInArray   true                      if  putInArray                backgroundImageArray backgroundImageArray length    backgroundImage                          backgroundLoading 1

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you can load images in your html somewhere using css display none  rule  then show them when you want with js or jquery  don t use js or jquery functions to preload is just a css rule Vs many lines of js to be executed  example  Html   lt img src  someimg png  class  hide  alt     gt    Css    hide  display none      jQuery     if want to show img      hide   show      if want to hide     hide   hide      Preloading images by jquery javascript is not good cause images takes few milliseconds to load in page   you have milliseconds for the script to be parsed and executed  expecially then if they are big images  so hiding them in hml is better also for performance  cause image is really preloaded without beeing visible at all  until you show that

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JP  After checking your solution  I was still having issues in Firefox where it wouldn t preload the images before moving along with loading the page  I discovered this by putting some sleep 5  in my server side script  I implemented the following solution based off yours which seems to solve this   Basically I added a callback to your jQuery preload plugin  so that it gets called after all the images are properly loaded      Helper function  used below     Usage    img1 jpg   img2 jpg   remove  img1 jpg    Array prototype remove   function element      for  var i   0  i  lt  this length  i          if  this i     element    this splice i 1                Usage      img1 jpg   img2 jpg    preloadImages function               Callback function gets called after all images are preloaded   fn preloadImages   function callback      checklist   this toArray      this each function             lt img gt    attr   src  this    load function           checklist remove   this  attr  src           if  checklist length    0    callback                         Out of interest  in my context  I m using this as follows     post   submit stuff     id  123    function response         response imgsrc1  response imgsrc2   preloadImages function           Update page with response data             Hopefully this helps someone who comes to this page from Google  as I did  looking for a solution to preloading images on Ajax calls

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A quick  plugin-free way to preload images in jQuery and get a callback function is to create multiple img tags at once and count the responses  e g   function preload files  cb        var len   files length        files map function f            return   lt img src    f      gt           join      load function              if --len   0                cb                         preload   one jpg    two png    three png    function            Code here is called once all files are loaded                  Note that if you want to support IE7  you ll need to use this slightly less pretty version  Which also works in other browsers    function preload files  cb        var len   files length          map files  function f            return   lt img src    f      gt           join      load function              if --len   0                cb

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I wanted to do this with a Google Maps API custom overlay  Their sample code simply uses JS to insert IMG elements and the image placeholder box is displayed until the image is loaded  I found an answer here that worked for me   https   stackoverflow com a 10863680 2095698        lt img src     imgPaht     gt    load function       this  width some  height some  appendTo   some target          This preloads an image as suggested before  and then uses the handler to append the img object after the img URL is loaded  jQuery s documentation warns that cached images don t work well with this eventing handler code  but it s working for me in FireFox and Chrome  and I don t have to worry about IE

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I wanted to do this with a Google Maps API custom overlay  Their sample code simply uses JS to insert IMG elements and the image placeholder box is displayed until the image is loaded  I found an answer here that worked for me   https   stackoverflow com a 10863680 2095698        lt img src     imgPaht     gt    load function       this  width some  height some  appendTo   some target          This preloads an image as suggested before  and then uses the handler to append the img object after the img URL is loaded  jQuery s documentation warns that cached images don t work well with this eventing handler code  but it s working for me in FireFox and Chrome  and I don t have to worry about IE

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This one line jQuery code creates  and loads  a DOM element img without showing it       lt img src  img 1 jpg   gt

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5 lines in coffeescript  array      img movie1 png    img movie2 png    img movie3 png      document  ready - gt    for index  image of array     img index    new Image       img index  src   image

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Here s a tweaked version of the first response that actually loads the images into DOM and hides it by default   function preload arrayOfImages          arrayOfImages  each function                  lt img   gt    attr  src  this  appendTo  body   css  display   none

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Quick and easy   function preload arrayOfImages          arrayOfImages  each function                lt img  gt    0  src   this             Alternatively you could use              new Image    src   this                Usage   preload        img imageName jpg        img anotherOne jpg        img blahblahblah jpg        Or  if you want a jQuery plugin     fn preload   function         this each function                lt img  gt    0  src   this                Usage       img1 jpg   img2 jpg   img3 jpg    preload

User · Answer

For those who know a little bit of actionscript  you can check for flash player  with minimal effort  and make a flash preloader  that you can also export to html5 Javascript Jquery  To use if the flash player is not detected  check examples on how to do this with the youtube role back to html5 player   And create your own  I do not have the details  becouse i have not started yet  if i dont forgot  i wil post it later and will try out some standerd Jquery code to mine

User · Answer

Thanks for this  I d liek to add a little riff on the J-P s answer - I don t know if this will help anyone  but this way you don t have to create an array of images  and you can preload all your large images if you name your thumbs correctly  This is handy because I have someone who is writing all the pages in html  and it ensures one less step for them to do - eliminating the need to create the image array  and another step where things could get screwed up      img   each function        var imgsrc     this  attr  src        if imgsrc match   th jpg      imgsrc match   home jpg           imgsrc   thumbToLarge imgsrc          new Image    src   imgsrc                 Basically  for each image on the page it grabs the src of each image  if it matches certain criteria  is a thumb  or home page image  it changes the name a basic string replace in the image src   then loads the images   In my case the page was full of thumb images all named something like image th jpg  and all the corresponding large images are named image lg jpg  The thumb to large just replaces the  th jpg with  lg jpg and then preloads all the large images   Hope this helps someone

User · Answer

JP  After checking your solution  I was still having issues in Firefox where it wouldn t preload the images before moving along with loading the page  I discovered this by putting some sleep 5  in my server side script  I implemented the following solution based off yours which seems to solve this   Basically I added a callback to your jQuery preload plugin  so that it gets called after all the images are properly loaded      Helper function  used below     Usage    img1 jpg   img2 jpg   remove  img1 jpg    Array prototype remove   function element      for  var i   0  i  lt  this length  i          if  this i     element    this splice i 1                Usage      img1 jpg   img2 jpg    preloadImages function               Callback function gets called after all images are preloaded   fn preloadImages   function callback      checklist   this toArray      this each function             lt img gt    attr   src  this    load function           checklist remove   this  attr  src           if  checklist length    0    callback                         Out of interest  in my context  I m using this as follows     post   submit stuff     id  123    function response         response imgsrc1  response imgsrc2   preloadImages function           Update page with response data             Hopefully this helps someone who comes to this page from Google  as I did  looking for a solution to preloading images on Ajax calls

User · Answer

5 lines in coffeescript  array      img movie1 png    img movie2 png    img movie3 png      document  ready - gt    for index  image of array     img index    new Image       img index  src   image

User · Answer

Quick and easy   function preload arrayOfImages          arrayOfImages  each function                lt img  gt    0  src   this             Alternatively you could use              new Image    src   this                Usage   preload        img imageName jpg        img anotherOne jpg        img blahblahblah jpg        Or  if you want a jQuery plugin     fn preload   function         this each function                lt img  gt    0  src   this                Usage       img1 jpg   img2 jpg   img3 jpg    preload

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I use the following code       myImage   attr  src   img spinner gif     var img   new Image      img  load function             myImage   attr  src  img src       img src    http   example com imageToPreload jpg

User · Answer

I would use an Manifest file to tell  modern  web browsers to also load all relevant images and cache them  Use Grunt and grunt-manifest to do this automatically and never worry again about preload scripts  cache invalidators  CDN etc    https   github com gunta grunt-manifest

User · Answer

Here s a tweaked version of the first response that actually loads the images into DOM and hides it by default   function preload arrayOfImages          arrayOfImages  each function                  lt img   gt    attr  src  this  appendTo  body   css  display   none

User · Answer

A quick  plugin-free way to preload images in jQuery and get a callback function is to create multiple img tags at once and count the responses  e g   function preload files  cb        var len   files length        files map function f            return   lt img src    f      gt           join      load function              if --len   0                cb                         preload   one jpg    two png    three png    function            Code here is called once all files are loaded                  Note that if you want to support IE7  you ll need to use this slightly less pretty version  Which also works in other browsers    function preload files  cb        var len   files length          map files  function f            return   lt img src    f      gt           join      load function              if --len   0                cb

User · Answer

you can load images in your html somewhere using css display none  rule  then show them when you want with js or jquery  don t use js or jquery functions to preload is just a css rule Vs many lines of js to be executed  example  Html   lt img src  someimg png  class  hide  alt     gt    Css    hide  display none      jQuery     if want to show img      hide   show      if want to hide     hide   hide      Preloading images by jquery javascript is not good cause images takes few milliseconds to load in page   you have milliseconds for the script to be parsed and executed  expecially then if they are big images  so hiding them in hml is better also for performance  cause image is really preloaded without beeing visible at all  until you show that

User · Answer

jQuery preloadImage function src onSuccess onError                var img   new Image           img src src          var error false          img onerror function                error true              if onError onError call img                     if error  false              setTimeout function                if img height gt 0 amp  amp img width gt 0                    if onSuccess onSuccess call img                   return img                  else                   setTimeout arguments callee 5                              0           return img              jQuery preloadImages function arrayOfImages           jQuery each arrayOfImages function                jQuery preloadImage this                        example        jQuery preloadImage           img someimage jpg           function                  complete             this width  0    true                                   function                  error

User · Answer

I have a small plugin that handles this   It s called waitForImages and it can handle img elements or any element with a reference to an image in the CSS  e g  div   background  url img png      If you simply wanted to load all images  including ones referenced in the CSS  here is how you would do it        body   waitForImages       waitForAll  true      finished  function               All images have loaded

User · Answer

I use the following code       myImage   attr  src   img spinner gif     var img   new Image      img  load function             myImage   attr  src  img src       img src    http   example com imageToPreload jpg

User · Answer

fn preload   function  callback      var length   this length    var iterator   0     return this each function          var self   this      var tmp   new Image         if  callback  tmp onload   function            callback call self  100     iterator   length  iterator     length               tmp src   this src             The usage is quite simple      img   preload function perc  done      console log this  perc  done         http   jsfiddle net yckart ACbTK

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fn preload   function  callback      var length   this length    var iterator   0     return this each function          var self   this      var tmp   new Image         if  callback  tmp onload   function            callback call self  100     iterator   length  iterator     length               tmp src   this src             The usage is quite simple      img   preload function perc  done      console log this  perc  done         http   jsfiddle net yckart ACbTK

User · Answer

I would use an Manifest file to tell  modern  web browsers to also load all relevant images and cache them  Use Grunt and grunt-manifest to do this automatically and never worry again about preload scripts  cache invalidators  CDN etc    https   github com gunta grunt-manifest

User · Answer

this jquery imageLoader plugin is just 1 39kb  usage         imageLoader       images   src1 src2 src3          allcomplete function e ui             images are ready here           your code - site fadeIn   or something like that             there are also other options like whether you want to load the images synchronously or asychronously and a complete event for each individual image

User · Answer

Quick and easy   function preload arrayOfImages          arrayOfImages  each function                lt img  gt    0  src   this             Alternatively you could use              new Image    src   this                Usage   preload        img imageName jpg        img anotherOne jpg        img blahblahblah jpg        Or  if you want a jQuery plugin     fn preload   function         this each function                lt img  gt    0  src   this                Usage       img1 jpg   img2 jpg   img3 jpg    preload

User · Answer

Quick and easy   function preload arrayOfImages          arrayOfImages  each function                lt img  gt    0  src   this             Alternatively you could use              new Image    src   this                Usage   preload        img imageName jpg        img anotherOne jpg        img blahblahblah jpg        Or  if you want a jQuery plugin     fn preload   function         this each function                lt img  gt    0  src   this                Usage       img1 jpg   img2 jpg   img3 jpg    preload

User · Answer

I usually use this snippet of code on my projects for the loading of the images in a page  You can see the result here https   jsfiddle net ftor34ey    lt script src  https   ajax googleapis com ajax libs jquery 3 5 1 jquery min js  gt  lt  script gt    lt img src  https   live staticflickr com 65535 50020763321 d61d49e505 k d jpg  width  100    gt   lt img src  https   live staticflickr com 65535 50021019427 692a8167e9 k d jpg  width  100    gt   lt img src  https   live staticflickr com 65535 50020228418 d730efe386 k d jpg  width  100    gt   lt img src  https   live staticflickr com 65535 50020230828 7ef175d07c k d jpg  width  100    gt    lt div style  background-image  url https   live staticflickr com 65535 50020765826 e8da0aacca k d jpg    gt  lt  div gt   lt style gt       bg           background-image  url  https   live staticflickr com 65535 50020765651 af0962c22e k d jpg           lt  style gt   lt div class  bg  gt  lt  div gt    lt div id  loadingProgress  gt  lt  div gt    The script save in an array all the src and background-image of the page and load all of them   You can see read show the progress of the loading by the var loadCount   let backgroundImageArray        function backgroundLoading i         let loadCount   0       let img   new Image          img  on  load   function               if  i  lt  backgroundImageArray length                 loadCount   parseInt   100   backgroundImageArray length    i                backgroundLoading i   1              else                loadCount   100                 do something when the page finished to load all the images             console log  loading completed                       loadingProgress   append   lt div gt loading completed    lt  div gt                         console log loadCount                     loadingProgress   append   lt div gt     loadCount      lt  div gt             attr  src   backgroundImageArray i - 1          document  ready function                  each function               var backgroundImage     this  css  background-image            var putInArray   false           var check   backgroundImage substr 0  3            if  check     url                  backgroundImage   backgroundImage split  url    join     split      join                  backgroundImage   backgroundImage replace                       backgroundImage   backgroundImage replace                        if  backgroundImage substr 0  4      http                     backgroundImage   backgroundImage                            putInArray   true             else if    this  get 0  tagName     IMG                  backgroundImage     this  attr  src                putInArray   true                      if  putInArray                backgroundImageArray backgroundImageArray length    backgroundImage                          backgroundLoading 1

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Use JavaScript Image object   This function allows you to trigger a callback upon loading all pictures  However  note that it will never trigger a callback if at least one resource is not loaded  This can be easily fixed by implementing onerror callback and incrementing loaded value or handling the error   var preloadPictures   function pictureUrls  callback        var i          j          loaded   0       for  i   0  j   pictureUrls length  i  lt  j  i               function  img  src                img onload   function                                                     if    loaded    pictureUrls length  amp  amp  callback                        callback                                                     Use the following callback methods to debug                in case of an unexpected behavior              img onerror   function                    img onabort   function                     img src   src             new Image    pictureUrls i               preloadPictures   http   foo picture bar    http   foo picture bar    http   foo picture bar    http   foo picture bar    function        console log  a         preloadPictures   http   foo picture bar    http   foo picture bar    http   foo picture bar    http   foo picture bar    function        console log  b

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Use JavaScript Image object   This function allows you to trigger a callback upon loading all pictures  However  note that it will never trigger a callback if at least one resource is not loaded  This can be easily fixed by implementing onerror callback and incrementing loaded value or handling the error   var preloadPictures   function pictureUrls  callback        var i          j          loaded   0       for  i   0  j   pictureUrls length  i  lt  j  i               function  img  src                img onload   function                                                     if    loaded    pictureUrls length  amp  amp  callback                        callback                                                     Use the following callback methods to debug                in case of an unexpected behavior              img onerror   function                    img onabort   function                     img src   src             new Image    pictureUrls i               preloadPictures   http   foo picture bar    http   foo picture bar    http   foo picture bar    http   foo picture bar    function        console log  a         preloadPictures   http   foo picture bar    http   foo picture bar    http   foo picture bar    http   foo picture bar    function        console log  b

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This works for me even in IE9       lt img src      imgURL       gt    on  load   function    doOnLoadStuff

User · Answer

function preload imgs          imgs  each function index  value                lt img   gt    attr  src   value  appendTo  body   css  display    none                 attr  src  value  not  attr  src  this   just to point it out

User · Answer

Thanks for this  I d liek to add a little riff on the J-P s answer - I don t know if this will help anyone  but this way you don t have to create an array of images  and you can preload all your large images if you name your thumbs correctly  This is handy because I have someone who is writing all the pages in html  and it ensures one less step for them to do - eliminating the need to create the image array  and another step where things could get screwed up      img   each function        var imgsrc     this  attr  src        if imgsrc match   th jpg      imgsrc match   home jpg           imgsrc   thumbToLarge imgsrc          new Image    src   imgsrc                 Basically  for each image on the page it grabs the src of each image  if it matches certain criteria  is a thumb  or home page image  it changes the name a basic string replace in the image src   then loads the images   In my case the page was full of thumb images all named something like image th jpg  and all the corresponding large images are named image lg jpg  The thumb to large just replaces the  th jpg with  lg jpg and then preloads all the large images   Hope this helps someone

User · Answer

function preload imgs          imgs  each function index  value                lt img   gt    attr  src   value  appendTo  body   css  display    none                 attr  src  value  not  attr  src  this   just to point it out

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