Detect Enter key is pressed with jQuery

<input type="text" id="txt">

$('#txt').keydown(function (e) {
    if (e.keyCode == 13) {
        alert('you pressed enter ^_^');
    }
})

On jsfiddle.

Update (June 2022)

Note that keyCode has been deprecated. Use KeyboardEvent.code or KeyboardEvent.key properties instead:

if (e.key === "Enter") {
   // Pressed enter
}