SO - 13831601

HTML

<div class="click">Click me to Disable/Enable a html button</div>
<div class="showup">
    <input id="Button" type="button" value=" + " style="background-color:grey" />
</div>

CSS

.showup {
    width: 100px;
    height: 100px;
}

.click {
    cursor: pointer;
    padding-bottom: 10px;
}

JavaScript

// Demo using plain javascript
var button = document.getElementById("Button");
var clickBtn = document.getElementsByClassName('click')[0];

// Disable the button on initial page load
button.disabled = true;

//add event listener
clickBtn.addEventListener('click', function(event) {
    button.disabled = !button.disabled;
});

button.addEventListener('click', function(event) {
    alert('Enabled!');
});