Delete all discord messages from DM or server automatically

// IMcPwn/delete-all-messages.js forked from niahoo/delete-all-messages.js
// Turn on Developer Mode under User Settings > Appearance > Developer Mode (at the bottom)
// Then open the channel you wish to delete all of the messages (could be a DM) and click the three dots on the far right.
// Click "Copy ID" and paste that instead of LAST_MESSAGE_ID.
// Copy / paste the below script into the JavaScript console.
// If you're in a DM you will receive a 403 error for every message the other user sent (you don't have permission to delete their messages).

var before = 'LAST_MESSAGE_ID';
clearMessages = function(){
    const authToken = document.body.appendChild(document.createElement`iframe`).contentWindow.localStorage.token.replace(/"/g, "");
    const channel = window.location.href.split('/').pop();
    const baseURL = `https://discordapp.com/api/channels/${channel}/messages`;
    const headers = {"Authorization": authToken };

    let clock = 0;
    let interval = 500;

    function delay(duration) {
        return new Promise((resolve, reject) => {
            setTimeout(() => resolve(), duration);
        });
    }

    fetch(baseURL + '?before=' + before + '&limit=100', {headers})
        .then(resp => resp.json())
        .then(messages => {
        return Promise.all(messages.map((message) => {
            before = message.id;
            return delay(clock += interval).then(() => fetch(`${baseURL}/${message.id}`, {headers, method: 'DELETE'}));
        }));
    }).then(() => clearMessages());
}
clearMessages();