JS判断用户连续输入

方案1

//
// $('#element').donetyping(callback[, timeout=1000])
// Fires callback when a user has finished typing. This is determined by the time elapsed
// since the last keystroke and timeout parameter or the blur event--whichever comes first.
//   @callback: function to be called when even triggers
//   @timeout:  (default=1000) timeout, in ms, to to wait before triggering event if not
//              caused by blur.
// Requires jQuery 1.7+
//
;(function($){
    $.fn.extend({
        donetyping: function(callback,timeout){
            timeout = timeout || 1e3; // 1 second default timeout
            var timeoutReference,
                doneTyping = function(el){
                    if (!timeoutReference) return;
                    timeoutReference = null;
                    callback.call(el);
                };
            return this.each(function(i,el){
                var $el = $(el);
                // Chrome Fix (Use keyup over keypress to detect backspace)
                // thank you @palerdot
                $el.is(':input') && $el.on('keyup keypress',function(e){
                    // This catches the backspace button in chrome, but also prevents
                    // the event from triggering too premptively. Without this line,
                    // using tab/shift+tab will make the focused element fire the callback.
                    if (e.type=='keyup' && e.keyCode!=8) return;

                    // Check if timeout has been set. If it has, "reset" the clock and
                    // start over again.
                    if (timeoutReference) clearTimeout(timeoutReference);
                    timeoutReference = setTimeout(function(){
                        // if we made it here, our timeout has elapsed. Fire the
                        // callback
                        doneTyping(el);
                    }, timeout);
                }).on('blur',function(){
                    // If we can, fire the event since we're leaving the field
                    doneTyping(el);
                });
            });
        }
    });
})(jQuery);

$('#example').donetyping(function(){
  $('#example-output').text('Event last fired @ ' + (new Date().toUTCString()));
});<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<input type="text" id="example" />
<p id="example-output">Nothing yet</p>

方案2.

https://github.com/kenshin54/jquery-koala

Load jQuery and koala:

<script src="jquery.min.js" type="text/javascript"></script>
<script src="jquery.koala.js" type="text/javascript"></script>

Bind keyboard events to the dom with Koala.

<script type="text/javascript">
   jQuery(document).ready(function() {
    $('.koala').koala({
      delay: 200,
      keyup: function(event){
        // do anything you want
        // ex. ajax
      }
    });
   });
</script>

Koala support descendant elements that are added to the document at a later time.

<script type="text/javascript">
   jQuery(document).ready(function() {
    $("#future").koala('.koala', {
      delay: 300,
      keyup: function(event){
        // do anything you want
        // ex. ajax
      }
    });
   });
</script>