Abort new AJAX request before completing the previous one

 var currentRequest = null;    

currentRequest = jQuery.ajax({
    type: 'POST',
    data: 'value=" + text,
    url: "AJAX_URL',
    beforeSend : function()    {           
        if(currentRequest != null) {
            currentRequest.abort();
        }
    },
    success: function(data) {
        // Success
    },
    error:function(e){
      // Error
    }
});