Adds a button to the kittysplit new entry page that deselects all participants.

DeslectAll.js

// ==UserScript==
// @name         Kittysplit deseletc all buton
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Adds a deselect all button to the kittysplit add new expense screen.
// @author       You
// @match        *.kittysplit.com/*/entries/new/expense
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    addButton();
})();

function addButton () {
    var collection = document.getElementById('entry-expense-parties');
    var button = document.createElement('button');
    button.innerHTML = "Deselect All";
    button.type = 'button';
    button.onclick = deSelectAll;
    collection.insertBefore(button, collection.childNodes[0]);
}

function deSelectAll() {
    var boxes = document.getElementsByClassName('checkbox');

    for( i = 0; i < boxes.length; i++)
    {
        var checkbox = boxes[i].children[0].children[0];
        console.log(checkbox);
        checkbox.checked = false;
    }
}