Js asynchronous code of HTML pages

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DOM

Hello. Here is the problem of my code.
There is a html content with pages labels on the bottom , I can click the page labels, then the content changed.
I'm using js code to simulate this operation , click each page label , then fetch the content displayed and something like that.
BUT , It seemed the content did not updated immidiately , the content fetched repeat the first page.
The fetching operation should be done after the page content has been changed. I tried the 'Promise', seems not code correct, the result just not right.

What I have tried:

if(window.location.href.includes('https://www.hide-my-ip.com/proxylist.shtml')) {
    //overview each page label
    for( var i of document.querySelectorAll('span a.paginate_button')) {
        new Promise((resolve,reject) => {
            //simulate the clickin on page label
            i.click();
            //alert(i.innerText);
            resolve();
        }).then( () => {
            console.log("current page index :"+ document.querySelector('.current').innerText);
            //fetch the content of switched page
            for(var item of document.querySelector('table tbody').children) {
                item = item.children;
                console.log(item[0].innerText + ':' + item[1].innerText);
            }
        });
    };
}

As the comment referred , Mutation observer can somehow deal with it.

if(window.location.href.includes('https://www.hide-my-ip.com/proxylist.shtml')) {
    new MutationObserver(function(mutation,observer) {
        for(let mu of mutation) {
            //content fetch.
            if(mu.addedNodes.length > 0) {
                for(var item of document.querySelector('table tbody').children) {
                    item = item.children;
                    console.log(item[0].innerText + ':' + item[1].innerText);
                }
            }
        }
        
        //get next page label and click
        var curr_pageidx=parseInt(document.querySelector('.current').innerText);
        var next_pageidx=curr_pageidx+1;
        var page_nodes=document.querySelectorAll('span a.paginate_button');
        for(let idx=0;idx<page_nodes.length;idx++) {
            if(parseInt(page_nodes[idx].innerText) == next_pageidx) {
                page_nodes[idx].click();
                break;
            }
        }
    }).observe(document.querySelector('tbody'),{childList: true});        
}