Tampermonkey script run before page load

Question

I need to hide a section from an html page:

<h1 data-ng-show="!menuPinned && !isSaaS" class="logo floatLeft" aria-hidden="false"><span>XXX </span><span style="font-weight: bold;">XXX </span><span>XXXXX</span></h1>

The following code works fine in Chrome dev. tools

var ibmlogo = document.querySelectorAll('h1.logo.floatLeft');
ibmlogo[1].remove();

But when I load the page with the script active, the section (h1) won't disappear. I believe this is because when the script runs, the DOM has not been completed loaded yet, hence the script fails to find the selector.

I have tried many different things (e.g. window.onLoad) but still my script is not effective. Last attempt (failed) is the following:

var logo = document.querySelectorAll('h1.logo.floatLeft');
logo.onload = function() {removeLogo()};
function removeLogo(){
    console.log("### logo array lenght: " + logo.length);
    logo[1].remove();
};

Solution

Required:

• @run-at: document-start in userscript metablock.

  // ==UserScript==
  ..............
  // @run-at        document-start
  ..............
  // ==/UserScript==
  

Now with the above your options are:

1. Simply inject a style that hides the logo:

   (document.head || document.documentElement).insertAdjacentHTML('beforeend',
       '<style>h1.logo.floatLeft { display: none!important; }</style>');
   

2. Use MutationObserver to detect and delete the element immediately after it's added into DOM.

   • Modify elements immediately (not after page completely loads)?
   • How to change the HTML content as it's loading on the page ("rare elements" code)
   • Performance of MutationObserver to detect nodes in entire DOM.

   new MutationObserver(function(mutations) {
       // check at least two H1 exist using the extremely fast getElementsByTagName
       // which is faster than enumerating all the added nodes in mutations
       if (document.getElementsByTagName('h1')[1]) {
           var ibmlogo = document.querySelectorAll('h1.logo.floatLeft')[1];
           if (ibmlogo) {
               ibmlogo.remove();
               this.disconnect(); // disconnect the observer
           }
       }
   }).observe(document, {childList: true, subtree: true});
   // the above observes added/removed nodes on all descendants recursively
   

Comments

[hsan]

Wouldn't a user style (e.g. using Stylish) with h1.logo.floatLeft { display: none; } do the trick?

[gxvigo]

Thanks @woxxom, the first option does the trick even if I don't quite understand how. When the script run my element doesn't exist (I tested with document.querySelectorAll, so how can the insertAdjacentHTML inject something in a non existing node? And if it's create a node, when the page eventually loads, it shouldn't override my injected element?

[gxvigo]

Hi couldn't make he second option (much fancier) working, in your code I get a syntax error in the second to last line (can't understand why). I then tried the sample from mozilla web site and the code fails because the target is not an Node, and checking it, when I create the target the element doesn't exist (I even tried with 'html') and target is always null. . Cheers

[wOxxOm]

1. It's what CSS sheets are for 2. The code should work as-is, don't change document parameter in observe. Anyway, I'm not psychic, so I can't tell what happens in your browser