jQuery: vokablR

HTML

<h1>sein</h1>
<form>
    <input type="text" id=simple_present placeholder="simple present">
    <input type="text" id=simple_past placeholder="simple past">
    <input type="text" id=past_participle placeholder="past participle">
</form>
<div class="answer">Enter: be - was - been</div>

CSS

.answer {position:absolute; bottom:0}

JavaScript

var json = {
    "verbs": {
        "irregular": [{
            "infinitiv": 'sein',
            "simple_present": 'be',
            "simple_past": 'was',
            "past_participle": 'been'},
        {
            "infinitiv": 'schlagen',
            "simple_present": 'beat',
            "simple_past": 'beat',
            "past_participle": 'beaten'},
        {
            "infinitiv": 'werden',
            "simple_present": 'become',
            "simple_past": 'became',
            "past_participle": 'become'},
        {
            "infinitiv": 'anfangen',
            "simple_present": 'begin',
            "simple_past": 'began',
            "past_participle": 'begun'},
        {
            "infinitiv": 'beißen',
            "simple_present": 'bite',
            "simple_past": 'bit',
            "past_participle": 'bitten'}]
    }
};


$('input').on('keyup', function() {
    var count = 0;

    if (this.value === json.verbs.irregular[count++][this.id]) {
        $(this).prop('disabled', true).next().focus();
    }

    if ($('input:not(:disabled)').length === 0) {
        $('input').val('').prop('disabled', false).first().focus();
        $('h1').text(json.verbs.irregular[count++].infinitiv);
        alert(count);
    }
});