In SO chat, adds a label indicating the character count of your message

char_count_adder.user.js

// ==UserScript==
// @name        char count adder (SO Chat)
// @namespace   .
// @description Adds a label indicating the character count of your message
// @include     http://chat.stackoverflow.com/rooms/*
// @include     https://chat.stackoverflow.com/rooms/*
// @version     3
// @grant       none
// ==/UserScript==

var max_one_liner = 150;
var max = 500;

var row = document.getElementById("chat-buttons");
var box = document.createElement("span");
row.appendChild(box);

function update_box(){
    var size = document.getElementById("input").value.length;
    var message = " " + size + " char" + (size==1 ? "" : "s");
    if (size == 0){
        message = "";
    }
    else if (size > max){
        message += " (Too large to submit by " + (size - max) + ")";
    }
    else if (size > max_one_liner){
        message += " (Too large to fit starred list by " + (size - max_one_liner) + ")";
    }
    box.innerHTML = message;
}
window.setInterval(update_box, 100);