Makes selling a ton of steam trading cards easier! Use as a bookmarklet (oneline it yourself) or declare it in the tab and call it.

steam_sell.js

if(!window.sell) {window.sell=()=>{
    /*Steam always has two items in the DOM, the for loop finds the one that's real*/
    let items = document.getElementsByClassName('inventory_iteminfo'), index = 0;
    for(let i = 0; i < items.length; i++) {
        if(items[i].style.display === "") {index = i; break;}
    }
    let page = Number(document.getElementById('pagecontrol_cur').innerText);
    /*Check if we can sell the item*/
    if(document.getElementById('iteminfo' + index + '_item_market_actions').style.display !== "none") {
        console.log('selling');
        let price = Number(
            document.getElementById(
                'iteminfo' + index + '_item_market_actions').childNodes[0].childNodes[1].innerText.replace(/(\r\n|\n|\r)/gm,' ').replace(/\$/gm,'').split(' ')[2]) * 100 - 2; /*Gets the price and subtracts two cents*/
        if(price + 0.02 >= 0.20){
            console.log("high value item!!");
            return;
        }
        SellCurrentSelection(); /*Function exposed by steam*/
        document.getElementById('market_sell_currency_input').value = "$" + (price / 100);
        let checkbox = document.getElementById('market_sell_dialog_accept_ssa');
        if(!checkbox.checked){checkbox.click()};
        let sell = document.getElementById('market_sell_dialog_accept');
        sell.click();sell.click();
        document.getElementById('market_sell_dialog_ok').click();
    } else {
        console.log('gemming');
        document.getElementById('iteminfo' + index + '_item_scrap_link').click();
        setTimeout(()=>{
            document.getElementsByClassName('newmodal_buttons')[0].firstChild.click();
            setTimeout(() => {
                document.getElementsByClassName('newmodal_buttons')[0].firstChild.click()
            }, 500);
        }, 500);
    }
    /*Scroll back*/
    setTimeout(()=>{console.log('done waiting')}, 1E4);
    for(let i = 1; i < page; i++) {
        document.getElementById('pagebtn_next').click();
    }
}}