<input type="button">

<input> elements of type "button" are rendered as simple push buttons, which can be programmed to control custom functionality anywhere on a webpage as required when assigned an event handler function (typically for the click event).

<input type="button" value="Click Me">

Value

An <input type="button"> elements' value attribute contains a DOMString that is used as the button's label.

<input type="button" value="Click Me">

If you don't specify a value, you get an empty button:

<input type="button">

Using buttons

<input type="button"> elements have no default behavior (their cousins, <input type="submit"> and <input type="reset"> are used to submit and reset forms, respectively). To make buttons do anything, you have to write JavaScript code to do the work.

A simple button

We'll begin by creating a simple button with a click event handler that starts our machine (well, it toggles the value of the button and the text content of the following paragraph):

<form> 
  <input type="button" value="Start machine">
</form>
<p>The machine is stopped.</p>

var btn = document.querySelector('input');
var txt = document.querySelector('p');

btn.addEventListener('click', updateBtn);

function updateBtn() {
  if (btn.value === 'Start machine') {
    btn.value = 'Stop machine';
    txt.textContent = 'The machine has started!';
  } else {
    btn.value = 'Start machine';
    txt.textContent = 'The machine is stopped.';
  }
}

The script gets a reference to the HTMLInputElement object representing the <input> in the DOM, saving this refence in the variable btn. addEventListener() is then used to establish a function that will be run when click events occur on the button.

Adding keyboard shortcuts to buttons

Keyboard shortcuts, also known as access keys and keyboard equivalents, let the user trigger a button using a key or combination of keys on the keyboard. To add a keyboard shortcut to a button — just as you would with any <input> for which it makes sense — you use the accesskey global attribute.

In this example, s is specified as the access key (you'll need to press s plus the particular modifier keys for your browser/OS combination; see accesskey for a useful list of those).

<form>
  <input type="button" value="Start machine" accesskey="s">
</form>
<p>The machine is stopped.</p>

Disabling and enabling a button

To disable a button, simply specify the disabled global attribute on it, like so:

<input type="button" value="Disable me" disabled>

You can enable and disable buttons at run time by simply setting disabled to true or false. In this example our button starts off enabled, but if you press it, it is disabled using btn.disabled = true. A setTimeout() function is then used to rest the button back to its enabled state after two seconds.

If the disabled attribute isn't specified, the button inherits its disabled state from its parent element. This makes it possible to enable and disable groups of elements all at once by enclosing them in a container such as a <fieldset> element, and then setting disabled on the container.

The example below shows this in action. This is very similar to the previous example, except that the disabled attribute is set on the <fieldset> when the first button is pressed — this causes all three buttons to be disabled until the two second timeout has passed.

Validation

Buttons don't participate in constraint validation; they have no real value to be constrained.

Examples

The below example shows a very simple drawing app created using a <canvas> element and some simple CSS and JavaScript (we'll hide the CSS for brevity). The top two controls allow you to choose the color and size of the drawing pen. The button, when clicked, invokes a function that clears the canvas.

<div class="toolbar">
  <input type="color" aria-label="select pen color">
  <input type="range" min="2" max="50" value="30" aria-label="select pen size"><span class="output">30</span>
  <input type="button" value="Clear canvas">
</div>

<canvas class="myCanvas">
  <p>Add suitable fallback here.</p>
</canvas>

var canvas = document.querySelector('.myCanvas');
var width = canvas.width = window.innerWidth;
var height = canvas.height = window.innerHeight-85;
var ctx = canvas.getContext('2d');

ctx.fillStyle = 'rgb(0,0,0)';
ctx.fillRect(0,0,width,height);

var colorPicker = document.querySelector('input[type="color"]');
var sizePicker = document.querySelector('input[type="range"]');
var output = document.querySelector('.output');
var clearBtn = document.querySelector('input[type="button"]');

// covert degrees to radians
function degToRad(degrees) {
  return degrees * Math.PI / 180;
};

// update sizepicker output value

sizePicker.oninput = function() {
  output.textContent = sizePicker.value;
}

// store mouse pointer coordinates, and whether the button is pressed
var curX;
var curY;
var pressed = false;

// update mouse pointer coordinates
document.onmousemove = function(e) {
  curX = (window.Event) ? e.pageX : e.clientX + (document.documentElement.scrollLeft ? document.documentElement.scrollLeft : document.body.scrollLeft);
  curY = (window.Event) ? e.pageY : e.clientY + (document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop);
}

canvas.onmousedown = function() {
  pressed = true;
};

canvas.onmouseup = function() {
  pressed = false;
}

clearBtn.onclick = function() {
  ctx.fillStyle = 'rgb(0,0,0)';
  ctx.fillRect(0,0,width,height);
}

function draw() {
  if(pressed) {
    ctx.fillStyle = colorPicker.value;
    ctx.beginPath();
    ctx.arc(curX, curY-85, sizePicker.value, degToRad(0), degToRad(360), false);
    ctx.fill();
  }

  requestAnimationFrame(draw);
}

draw();

Specifications

Browser compatibility

See also

• <input> and the HTMLInputElement interface which implements it.
• The more modern <button> element.