Load jQuery with Javascript and use jQuery

Question

I am appending the jQuery library to the dom using    var script   document createElement  script     script src    https   ajax googleapis com ajax libs jquery 1 7 1 jquery min js    script type    text javascript    document getElementsByTagName  head   0  appendChild script     However when I run   jQuery document  ready function         The console reports the error   Uncaught ReferenceError  jQuery is not defined   How do I load jQuery dynamically as well as use it once it is in the dom

User · Answer

From the DevTools console  you can run   document getElementsByTagName  head   0  innerHTML      lt script type  text javascript  src    ajax googleapis com ajax libs jquery 3 4 1 jquery min js  gt  lt   script gt      Check the available jQuery version at https   code jquery com jquery    To check whether it s loaded  see  Checking if jquery is loaded using Javascript

User · Answer

HTML    lt html gt     lt head gt      lt  head gt     lt body gt        lt div id  status  gt jQuery is not loaded yet  lt  div gt       lt input type  button  value  Click here to load it   onclick  load      gt      lt  body gt   lt  html gt       Script       lt script gt           load   function               load getScript  jquery-1 7 2 js              load tryReady 0      We will write this function later  It s responsible for waiting until jQuery loads before using it                        dynamically load any javascript file          load getScript   function filename              var script   document createElement  script             script setAttribute  type   text javascript             script setAttribute  src   filename            if  typeof script   undefined             document getElementsByTagName  head   0  appendChild script                      lt  script gt

User · Answer

Using require js you can do the same thing in a safer way  You can just define your dependency on jquery and then execute the code you want using the dependency when it is loaded without polluting the namespace   I generally recommend this library for managing all dependencies on Javascript  It s simple and allows for an efficient optimization of resource loading  However there s some precautions you may need to take when using it with JQuery   My favourite way to deal with them is explained in this github repo and reflected by the following code sample    lt title gt jQuery RequireJS Sample Page lt  title gt      lt script src  scripts require js  gt  lt  script gt      lt script gt     require          baseUrl   scripts          paths               jquery   https   ajax googleapis com ajax libs jquery 1 6 0 jquery min                   priority    jquery            main          lt  script gt

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There s a working JSFiddle with a small example here  that demonstrates exactly what you are looking for  unless I ve misunderstood your request   http   jsfiddle net 9N7Z2 188   There are a few issues with that method of loading javascript dynamically  When it comes to the very basal frameworks  like jQuery  you actually probably want to load them statically  because otherwise  you would have to write a whole JavaScript loading framework     You could use some of the existing JavaScript loaders  or write your own by watching for window jQuery to get defined      Immediately-invoked function expression  function            Load the script     var script   document createElement  SCRIPT        script src    https   ajax googleapis com ajax libs jquery 1 7 1 jquery min js       script type    text javascript       script onload   function             var     window jQuery             Use   here               document getElementsByTagName  head   0  appendChild script           Just remember that if you need to support really old browsers  like IE8  load event handlers do not execute  In that case  you would need to poll for the existance of window jQuery using repeated window setTimeout  There is a working JSFiddle with that method here  http   jsfiddle net 9N7Z2 3   There are lots of people who have already done what you need to do  Check out some of the existing JavaScript Loader frameworks  like    https   developers google com loader   no longer documented  http   yepnopejs com   deprecated  http   requirejs org

User · Answer

There is an other way to load jQuery dynamically  source   You could also use   document write   lt script type  text javascript  src  http   ajax googleapis com ajax libs jquery 1 7 1 jquery min js  gt  lt   script gt       It s considered bad practice to use document write  but for sake of completion it s good to mention it   See Why is document write considered a  quot bad practice quot   for the reasons  The pro is that document write does block your page from loading other assests  so there is no need to create a callback function

User · Answer

The reason you are getting this error is that JavaScript is not waiting for the script to be loaded  so when you run   jQuery document  ready function         there is not guarantee that the script is ready  and never will be    This is not the most elegant solution but its workable   Essentially you can check every 1 second for the jQuery object ad run a function when its loaded with your code in it   I would add a timeout  say clearTimeout after its been run 20 times  as well to stop the check from occurring indefinitely    var jQueryIsReady   function          Your JQuery code here    var checkJquery   function        if typeof jQuery      undefined            return false       else          clearTimeout interval           jQueryIsReady            var interval   setInterval checkJquery 1000

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Encosia s website recommends    lt script type  text javascript           src  http   www google com jsapi  gt  lt  script gt   lt script type  text javascript  gt       You may specify partial version numbers  such as  1  or  1 3         with the same result  Doing so will automatically load the        latest version matching that partial revision pattern         e g  1 3 would load 1 3 2 today and 1 would load 1 7 2     google load  jquery    1 7 2       google setOnLoadCallback function            Place init code here instead of   document  ready          lt  script gt    But even he admits that it just doesn t compare to doing the following when it comes to optimal performance        lt script src    ajax aspnetcdn com ajax jQuery jquery-1 7 2 min js  type  text javascript  gt  lt  script gt       lt script type  text javascript  gt  window jQuery    document write   lt script src  js libs jquery-1 7 2 min js  gt  x3C script gt    lt  script gt       lt script type  text javascript  src  scripts js  gt  lt  scripts gt   lt  body gt   lt  html gt

User · Answer

You need to run your code AFTER jQuery finished loading var script   document createElement  script     document head appendChild script       script type    text javascript   script src    quot   ajax googleapis com ajax libs jquery 3 1 0 jquery min js quot   script onload   function           your jQuery code here      or if you re running it in an async function you could use await in the above code var script   document createElement  script     document head appendChild script       script type    text javascript   script src    quot   ajax googleapis com ajax libs jquery 3 1 0 jquery min js quot   await script onload    your jQuery code here  If you want to check first if jQuery already exists in the page  try this

[javascript] Load jQuery with Javascript and use jQuery

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