[danik.js]

<button id="button">Жми!</button>
<script>
    var button = document.getElementById('button');
    var actions = {
        1: function() {
           alert('Действие 1');
        },
        2: function() {
           alert('Действие 2');
        }
    };
    var counter = 0;
    button.onclick = function() {
        actions[counter = (counter % 2) + 1]();
    }
</script>