Question

112

Check if Javascript script exists on page

rated 0 times [ 119] [ 7] / answers: 1 / hits: 49034 / 12 Years ago, sun, march 11, 2012, 12:00:00

I have a bookmarklet that I've made and it loads a script from my server onto the users current page. However I have an if check in my script that if a condition is not met then no action is taken. However if the user then meets that condition then the code is run, but has caused there to be two sets of scripts inserted into their page. Can i prevent this?

 <a href=javascript: (function () {

    var jsCode = document.createElement('script');

    jsCode.setAttribute('src', 'http://xxx.co.uk/xxx/script.js');

  document.body.appendChild(jsCode);

 }());>Bookmarklet</a>

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

christianu

Add To Favorites

Follow

Total Points: 481

Total Questions: 124

Total Answers: 99

Location: Trinidad and Tobago

Member since Thu, Dec 1, 2022

2 Years ago

christianu questions

1 Having a trouble with Google OAuth2 (app has no backend, so client side only)

Mon, May 9, 22, 00:00, 2 Years ago

1 Change Icon on click with JS

Thu, Mar 10, 22, 00:00, 2 Years ago

1 Svelte: is there a way to cache the api result in a way that it won't trigger the api call everytime the component renders?

Sun, Sep 27, 20, 00:00, 4 Years ago

1 Javascript / React use of square brackets

Sun, Jul 5, 20, 00:00, 4 Years ago

1 Cannot POST to Express router (404 error)

Wed, Jun 17, 20, 00:00, 4 Years ago

View All

answered 12 Years ago cindyanyssam · Accepted Answer

You can check whether your script is loaded like this:

function isMyScriptLoaded(url) {

    if (!url) url = http://xxx.co.uk/xxx/script.js;

    var scripts = document.getElementsByTagName('script');

    for (var i = scripts.length; i--;) {

        if (scripts[i].src == url) return true;

    }

    return false;

}

Alternatively, you could do something like this:

<a href=javascript:

    if (!jsCode) {

        var jsCode = document.createElement('script');

        jsCode.setAttribute('src', 'http://xxx.co.uk/xxx/script.js');

        document.body.appendChild(jsCode);

    }

 >Bookmarklet</a>

This pollutes the global namespace with the jsCode variable, but that might be a necessary evil. You could rename it to something that is unlikely to appear in the document where the bookmarklet is run.

Please note that while the javascript URI scheme is okay for bookmarklets as in this case, it's not considered to be a good practice for normal use.