Dynamically create Bootstrap alerts box through JavaScript

/**
  Bootstrap Alerts -
  Function Name - showalert()
  Inputs - message,alerttype
  Example - showalert("Invalid Login","alert-error")
  Types of alerts -- "alert-error","alert-success","alert-info","alert-warning"
  Required - You only need to add a alert_placeholder div in your html page wherever you want to display these alerts "<div id="alert_placeholder"></div>"
  Written On - 14-Jun-2013
**/

  function showalert(message,alerttype) {

    $('#alert_placeholder').append('<div id="alertdiv" class="alert ' +  alerttype + '"><a class="close" data-dismiss="alert">×</a><span>'+message+'</span></div>')

    setTimeout(function() { // this will automatically close the alert and remove this if the users doesnt close it in 5 secs


      $("#alertdiv").remove();

    }, 5000);
  }

You can also create a HTML alert template like this:

<div class="alert alert-info" id="alert_template" style="display: none;">
    <button type="button" class="close">×</button>
</div>

And so you can do in JavaScript this here:

$("#alert_template button").after('<span>Some text</span>');
$('#alert_template').fadeIn('slow');

Which is in my opinion cleaner and faster. In addition you stick to Twitter Bootstrap standards when calling fadeIn().

To guarantee that this alert template works also with multiple calls (so it doesn't add the new message to the old one), add this here to your JavaScript:

$('#alert_template .close').click(function(e) {
    $("#alert_template span").remove();
});

So this call removes the span element every time you close the alert via the x-button.

Try this (see a working example of this code in jsfiddle: http://jsfiddle.net/periklis/7ATLS/1/)

<input type = "button" id = "clickme" value="Click me!"/>
<div id = "alert_placeholder"></div>
<script>
bootstrap_alert = function() {}
bootstrap_alert.warning = function(message) {
            $('#alert_placeholder').html('<div class="alert"><a class="close" data-dismiss="alert">×</a><span>'+message+'</span></div>')
        }

$('#clickme').on('click', function() {
            bootstrap_alert.warning('Your text goes here');
});
</script>​

EDIT: There are now libraries that simplify and streamline this process, such as bootbox.js

I created this VERY SIMPLE and basic plugin:

(function($){
    $.fn.extend({
        bs_alert: function(message, title){
            var cls='alert-danger';
            var html='<div class="alert '+cls+' alert-dismissable"><button type="button" class="close" data-dismiss="alert" aria-hidden="true">&times;</button>';
            if(typeof title!=='undefined' &&  title!==''){
                html+='<h4>'+title+'</h4>';
            }
            html+='<span>'+message+'</span></div>';
            $(this).html(html);
        },
        bs_warning: function(message, title){
            var cls='alert-warning';
            var html='<div class="alert '+cls+' alert-dismissable"><button type="button" class="close" data-dismiss="alert" aria-hidden="true">&times;</button>';
            if(typeof title!=='undefined' &&  title!==''){
                html+='<h4>'+title+'</h4>';
            }
            html+='<span>'+message+'</span></div>';
            $(this).html(html);
        },
        bs_info: function(message, title){
            var cls='alert-info';
            var html='<div class="alert '+cls+' alert-dismissable"><button type="button" class="close" data-dismiss="alert" aria-hidden="true">&times;</button>';
            if(typeof title!=='undefined' &&  title!==''){
                html+='<h4>'+title+'</h4>';
            }
            html+='<span>'+message+'</span></div>';
            $(this).html(html);
        }
    });
})(jQuery);

Usage is

<div id="error_container"></div>
<script>
$('#error_container').bs_alert('YOUR ERROR MESSAGE HERE !!', 'title');
</script>

first plugin EVER and it can be easily made better