jQuery addClass example

Change class name on click in jQuery

HTML

<div id="background">
    <h1 id="tittle" class="f1">Test</h1>
    <div id="atr">
      <h1 id="tittle2" class="f1 f2">math</h1>
    </div>
    <div id="atr" class="ahke">
      <button id="buttonstart">
        <a id="why" class="why2" href="#">Start</a>
      </button>

      <div id="mathbox">
        <div id="operaciones">
          <div id="atr54">

            <div class="op" id="num1"></div>

            <div class="op" id="operador"></div>
            <div class="op" id="num2"></div>
          </div>

        </div>
        <input id="resultado" type="number" placeholder="Answer">

CSS

/*! HTML5 Boilerplate v6.1.0 | MIT License | https://html5boilerplate.com/ */

/*
 * What follows is the result of much research on cross-browser styling.
 * Credit left inline and big thanks to Nicolas Gallagher, Jonathan Neal,
 * Kroc Camen, and the H5BP dev community and team.
 */

/* ==========================================================================
   Base styles: opinionated defaults
   ========================================================================== */

html {
    color: #222;
    font-size: 1em;
    line-height: 1.4;
}

/*
 * Remove text-shadow in selection highlight:
 * https://twitter.com/miketaylr/status/12228805301
 *
 * Vendor-prefixed and regular ::selection selectors cannot be combined:
 * https://stackoverflow.com/a/16982510/7133471
 *
 * Customize the background color to match your design.
 */

::-moz-selection {
    background: #b3d4fc;
    text-shadow: none;
}

::selection {
    background: #b3d4fc;
    text-shadow: none;
}

/*
 * A better looking default horizontal rule
 */

hr {
    display: block;
    height: 1px;
    border: 0;
    border-top: 1px solid #ccc;
    margin: 1em 0;
    padding: 0;
}

/*
 * Remove the gap between audio, canvas, iframes,
 * images, videos and the bottom of their containers:
 * https://github.com/h5bp/html5-boilerplate/issues/440
 */

audio,
canvas,
iframe,
img,
svg,
video {
    vertical-align: middle;
}

/*
 * Remove default fieldset styles.
 */

fieldset {
    border: 0;
    margin: 0;
    padding: 0;
}

/*
 * Allow only vertical resizing of textareas.
 */

textarea {
    resize: vertical;
}

/* ==========================================================================
   Browser Upgrade Prompt
   ========================================================================== */

.browserupgrade {
    margin: 0.2em 0;
    background: #ccc;
    color: #000;
    padding: 0.2em 0;
}

/* ==========================================================================
   Author's custom styles
  ...

JavaScript

var puntos = 0;
randomiseiconscycle1();

function randomiseiconscycle1() {
    $("#buttonstart").click(function() {
        $("#buttonstart").css("display", "none")
        $("#why").css("display", "none")
        $(".ahke").css("margin", "0")
        $("#atr").css("margin", "0")
        $(".f1").css("display", "none")
        $("#mathbox").show("slide", 1000);
    });
    var minNumber = 0;
    var maxNumber = 20;
    var randomNumber= 0;
           var randomNumber2= 0;
     randomNumber = randomNumberFromRange(minNumber, maxNumber);
     randomNumber2 = randomNumberFromRange(minNumber, maxNumber);

    function randomNumberFromRange(min, max) {
        return Math.floor(Math.random() * (max - min + 1) + min);
    }
    $("#num1").text(randomNumber);
    $("#operador").text("+");
    $("#num2").text(randomNumber2);
    var resultado = randomNumber + randomNumber2;
    $("#resultado").on("input", function() {
        var input = $('#resultado').val();
        if (input == resultado) {
            input = $('#resultado').val("");
            minNumber = 1;
            puntos += 1;
            maxNumber = 15;
            randomNumber= 0;
            randomNumber2= 0;
            randomNumber = randomNumberFromRange(minNumber, maxNumber);
            randomNumber2 = randomNumberFromRange(minNumber, maxNumber);
            $("#num1").text(randomNumber);
            $("#operador").text("-");
            $("#num2").text(randomNumber2);
             resultado = randomNumber - randomNumber2;
     
            if (input == resultado) {
                console.log("resta0");
                input = $('#resultado').val("");
                minNumber = 1;
                maxNumber = 8;
                puntos += 1;
                randomNumber= 0;
            randomNumber2= 0;
                randomNumber = randomNumberFromRange(minNumber, maxNumber);
                randomNumber2 = randomNumberFromRange(minNumber, maxNumber);
                $("#num1").text(randomNumber);
 ...