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MutationObserver wrapper to wait for the specified CSS selector
        此脚本不应直接安装。它是供其他脚本使用的外部库,要使用该库请加入元指令 // @require https://update.greasyfork.icu/scripts/12228/175122/setMutationHandler.js
      
A MutationObserver wrapper to wait for an element (or elements) with the specified CSS selector.
First, load the function in your script metablock:
.............. // @require http://greasyfork.icu/scripts/12228/code/setMutationHandler.js .............. // ==/UserScript==
Watch for added nodes:
setMutationHandler(document, '.container p.some-child', nodes => {
    nodes.forEach(node => node.style.display = 'none');
    return false; // disconnect the observer, this is useful for one-time jobs
});
The observation target parameter may be omitted so "document" will be used by default:
setMutationHandler('.container p.some-selector', nodes => { ...... });
Options form:
setMutationHandler({
    processExisting: true, // Process existing elements and watch for mutations from now on
    selector: '.container p.some-child',
    handler: nodes => nodes.forEach(node => node.style.display = 'none')
});
Watch for added nodes only inside the specified container element that already exists in the document:
setMutationHandler({
    target: document.querySelector('.container-selector'),
    selector: 'p.some-child',
    handler: nodes => nodes.forEach(node => node.style.display = 'none')
});
Advanced example with customized mutation options:
setMutationHandler({
    selector: '.container p.some-child',
    processExisting: false,       // optional
    target: document,             // optional
    childList: true,              // optional
    subtree: true,                // optional
    attributes: false,            // optional
    attributeFilter: [],          // optional
    attributeOldValue: false,     // optional
    characterData: false,         // optional
    characterDataOldValue: false, // optional
    handler: nodes => {
        console.log(nodes);
        return false; // disconnect the observer, this is useful for one-time jobs
    },
});
Make your userscript run at document-start to catch the mutations during page load:
.............. // @run-at document-start // @require http://greasyfork.icu/scripts/12228/code/setMutationHandler.js .............. // ==/UserScript==