Mewch Post Hiding Feature

//HIDER CSS
var showposts = 30;
setTimeout(function () {
    if (window.location.href.indexOf('res') !== -1) {
        dostuff();
    }
}, 1000);

function dostuff() {
    var hider = document.createElement('style');
    var magic = '.board-container .hider:after{content:"Show Hidden Posts"; color:red;} .board-container .hider:checked{content:"Hide Posts";} .board-container .hider:not(:checked) + .thread-container div:not(:nth-last-child(-n+'+showposts+')){display:none;} .thread-container .post-container:nth-child(1){display:block !important;}';
    hider.innerHTML = magic;
    document.head.appendChild(hider);

    var cssbutton = document.createElement('input');
    cssbutton.className = 'hider';
    cssbutton.style = 'width: 260px;';
    cssbutton.type = 'checkbox';
    var parent = document.getElementsByClassName('board-container')[0]
    parent.insertBefore(cssbutton, document.getElementsByClassName('thread-container')[0]);
}