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Select2

Select2 is a jQuery based replacement for select boxes. It supports searching, remote data sets, and infinite scrolling of results. Look and feel of Select2 is based on the excellent Chosen library.

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Warning!

This page refers to an unreleased version of Select2 which may be unstable. For the latest stable and previous versions please see links at the top. The code for this version is only available in the master branch.

Changelog

  • Support for selection of multiple values. See multiple option in the docs.
  • Ability to reset back to placeholder once a selection has been made. See allowClear option in the docs.
  • Simplified paging of remote datasets by tracking the page number automatically.
  • Minimum required jQuery version changed from 1.7+ to 1.4.2

Examples

The Basics

Select2 can take a regular select box like this:

and turns it into:


with support for quick option filtering via a search box

Example Code

<head>
    <link href="select2.css" rel="stylesheet"/>
    <script src="select2.js"></script>
    <script>
        $(document).ready(function() { $("#e1").select2(); });
    </script>
</head>
<body>
    <select id="e1">
        <option value="AL">Alabama</option>
        ...
        <option value="WY">Wyoming</option>
    </select>
</body>

Multi-Value Select Boxes

Select2 also supports multi-value select boxes. The select below is declared with the multiple attribute. Select2 automatially picks up on this:


Example Code

Placeholders

A placeholder value can be defined and will be displayed until a selection is made:


The placeholder can be declared via a data-placeholder attribute attached to the select, or via the placeholder configuration element as seen in the example code

Optionally, a clear button (visible once a selection is made) is available to reset the select box back to the placeholder value.

Example Code

Minimum Input

Select2 supports a minimum input setting which is useful for large remote datasets where short search terms are not very useful:


Example Code


         

        


        

          

            
Templating

             
Various display options of the Select2 component can be changed:

             

                 

             

          

          

            
Example Code

            

         

        


       

          

            
Loading Data

             
Select2 uses a function to load result data. Here is a trivial example that creates choices that consist of user's input repeated a number of times:

             

                 
             

             
In order to take advantage of custom data loading Select2 should be attached to an input type='hidden' tag, otherwise data is parsed from select's option tags.

          

          

            
Example Code

            
            

         

        


      

         

           
Loading Array Data

            
Select2 provides some shortcuts that make it easy to access local data stored in an array instead of having to write a query function mentioned in the example above.

            
Example below inlines the data by specifying an array in the data element. Items in such an array must have id and text keys.

            

                
            

            
If your data does not have a text key, an alternative key can be specified as a string:

             

                 
             

             
or as a function:

             

                 
             

         

         

           
Example Code

           
           

        

       

          
        

           

             
Loading Remote Data

              
Select2 comes with AJAX/JSONP support built in. In this example we will search for a movie using Rotten Tomatoes API:

              

                  
              

              
Example Code

              

              
Select2 uses jQuery's $.ajax function to execute the remote call by default. An alternative transport function can be specified in the ajax settings, or an entirely custom implementation can be built by providing a custom query function instead of using the ajax helper

           

        

        

            

              
Infinite Scroll with Remote Data

               
Select2 supports lazy-appending of results when the result list is scrolled to the end.
                   In order to enable the remote service must support some sort of a paging mechanism and
                   the query function given to Select2 must take advantage of it. The following example demonstrates
                   how this can be set up. Search for some keyword and then scroll the result list to the end to
                   see more results load:

               

                   
               

              
Example Code

              

            

         


        

          

            
Pragmatic Access

             
Select2 supports methods that allow pragmatic control of the componentL

             

                 

             

              

                
                
              

              

                  

              

               

                 
                 
               

          

          

            
Example Code

            

         

        


      


          

              
Change Event


              
Select2 triggers the change event on the original element whenever its value is changed by
                  the user


              


              


              

          

          

              
Example Code

           
           

          

      

      


          

              
Tagging Support


              
Select2 can be used to quickly set up fields used for tagging


              

              
Note that when tagging is enabled the user can select from pre-existing tags or create a new tag by
                  picking the first choice which is what the user has typed into the search box so far.

          

          

              
Example Code

           
           

          

      


      


          

              
Reacting to external value changes


              
Select2 can react to external value changes and keep its selection in-sync. This feature allows
                  Select2 to work seamlessly with front-end frameworks that use data binding between ui components
                  and model values.

              


              
 

              
This feature is only available when initSelection() function is provided in
                  the options. This function is needed to map the choice ids set on the element to objects used by
                  Select2. This function is set by default when Select2 is attached to a select or when
                  the tags helper function is used.

          

          

              
Example Code

           
           

          

      


      
      

      
      
      
      
      
      
      
      


        

            
Documentation

        


        

            
Constructor

        

        

            

                ParameterTypeDescription
            

            
minimumInputLengthintNumber of characters necessary to start a search

            
minimumResultsForSearchint
                

                    The minimum number of results that must be initially (after opening the dropdown for the first time)
                    populated in order to keep the search field. This
                    is useful for cases where local data is used with just a few results, in which case the search box
                    is not very useful and wastes screen space.
                

                
Only applies to single-value select boxes

            		
            

            
placeholderobject/string
                
Initial value that is selected if no other selection is made.

                

                    The value can be specified either as an object or as a string. If
                    specified as a string any custom formatSelection function will be
                    bypassed and the string value will be rendered directly.
                

                
The placeholder can also be specified as a data-placeholder attribute on the select
                    or input element that Select2 is attached to. In this case only string
                    values are supported
                


                
Note that because browsers assume the first option element
                    is selected in
                    non-multi-value select boxes an empty first option element must be provided (<option></option>)
                    for the placeholder to work.
                

            

            

                allowClear
                boolean
                
                    

                        Whether or not a clear button is displayed when the select box has a selection. The
                        button,
                        when clicked, resets the value of the select box back to the placeholder, thus this option is
                        only
                        available when the placeholder is specified.
                    


                    

                        Also, note that this option only works with
                        non-multi-value based selects because multi-value selects always provide such a button for every
                        selected option.
                    

                		
            

            

                multiple
                boolean
                
                    

                        Whether or not Select2 allows selection of multiple values.
                    

                    
When Select2 is attached to a select element this value will be ignored and select's
                        multiple attribute will be used instead.
                    

                		
            


            
formatSelectionfunction
                Function used to render the current selection.
                
formatSelection(object)

                

                    
ParameterTypeDescription

                    
objectobjectThe selected result object returned from the query function

                    
<returns>stringHtml that represents the selection

                

                The default implementation expects the object to have a text property that is returned.
            

            
formatResultfunction
                Function used to render a result that the user can select.
                
formatResult(object)

                

                    
ParameterTypeDescription

                    
objectobjectOne of the result objects returned from the query function

                    
<returns>stringHtml that represents the result

                

                The default implementation expects the object to have a text property that is returned.
            

            
formatNoMatchesfunction
                Function used to render the "No matches" message
                
formatNoMatches(term)

                

                    
ParameterTypeDescription

                    
termstringSearch string entered by user

                    
<returns>stringMessage html

                

            

            
formatInputTooShortfunction
                Function used to render the "Search input too short" message
                
formatInputTooShort(term, minLength)

                

                    
ParameterTypeDescription

                    
termstringSearch string entered by user

                    
minLengthintMinimum required term length

                    
<returns>stringMessage html

                

            

            
createSearchChoicefunction
                Creates a new selectable choice from user's search term. Allows creation of choices not available via the query
                function. Useful when the user can create choices on the fly, eg for the 'tagging' usecase.
                
createSearchChoice(term)

                

                    
ParameterTypeDescription

                    
termstringSearch string entered by user

                    
<returns>object (optional)Object representing the new choice.
                        Must at least contain an id attribute.

                

                If the function returns undefined or null no choice will be created. If a new
                choice is created it is displayed first in the selection list so that user may select it by simply pressing
                enter.
                
                
When used in combination with input[type=hidden] tag care
                must be taken to sanitize the id attribute of the choice object, especially stripping
                , as it is used as a value separator

            

            
initSelectionfunction
                Called when Select2 is created to allow the user to initialize the selection based on the value of the
                element select2 is attached to.
                

                Essentially this is an id->object mapping function.
                

                
initSelection(element)

                

                    
ParameterTypeDescription

                    
elementjQuery arrayelement Select2 is attached to

                    
<returns>object or array of objectsObject representing the choice
                        to be selected, or an array of such objects in case Select2 is in multi mode.

                

                
This function will only be called when there is initial input to be processed.

                Here is an example implementation used for tags. Tags are the simplest form of data where the id is also
                the text:

$("#tags").select2({
    initSelection : function (element) {
        var data = [];
        $(element.val().split(",")).each(function () {
            data.push({id: this, text: this});
        });
        return data;
    }
});


            

            

                query
                function
                
                    Function used to query results for the search term.
                    
query(options)

                    

                        
ParameterTypeDescription

                        
options.termstringSearch string entered by user

                        
options.pageint1-based page number tracked by Select2 for use with infinite scrolling of results

                        
options.callbackfunction
                            Callback function that should be called with the result object. The result object:
                                

                                    
ParameterTypeDescription

                                    
result.results[object]Array of result objects. The default renderers expect objects with id and text keys. The id attribute is required, even if custom renderers are used.

                                    
result.morebooleantrueif more results are available for the current search term

                                

                            

                    

                    
In order for this function to work Select2 should be attached to a input type='hidden' tag instead of a select.

                		
            

            
ajaxobject
                Options for the built in ajax query function. This object acts as a shortcut for having to manually write a function that performs ajax requests. The built-in function supports more advanced features such as throttling and dropping out-of-order responses.

                

                    
ParameterTypeDescription

                    
transportfunctionFunction that will be used to perform the ajax request. Must be parameter-compatible with $.ajax. Defaults to $.ajax if not specified.
                        Allows the use of various ajax wrapper libraries such as: AjaxManager. 

                    
urlstringAjax url

                    
dataTypestringtData type for the request. ajax, jsonp, other formats supported by jquery

                    
quietMillisintNumber of milliseconds to wait for the user to stop typing before issuing the ajax request

                    
datafunction
                        Function to generate query parameters for the ajax request.
                        
data(term, page)

                        

                            
ParameterTypeDescription

                            
termstringSearch term

                            
pageint1-based page number tracked by Select2 for use with infinite scrolling of results

                            
<returns>objectObject containing url paramters

                        

                    

                    
resultsfunction
                        Function used to build the query results object from the ajax response
                        
results(term, page)

                        

                            
ParameterTypeDescription

                            
termstringSearch term

                            
pageintPage number that was passed into the data function above

                            
<returns>objectResults object. See "options.callback" in the "query" function for format.

                        

                    

                

                
In order for this function to work Select2 should be attached to a input type='hidden' tag instead of a select.

            

            
dataarray/object
                Options for the built in query function that works with arrays.
                
If this element contains an array, each element in the array must contain id and text keys

                
Alternatively, this element can be specified as an object in which results key must contain the data as an array and a text key can either be the name of the key in data items that contains text or a function that retrieves the text given a data element from the array

            

            
tagsarray/function
                Puts Select2 into 'tagging'mode where the user can add new choices and pre-existing tags are provided via
                this options attribute which is either an array or a function that returns an
                array of objects or strings. If strings are used instead of objects
                they will be converted into an object that has an id and text attribute equal
                to the value of the string.
            

        


      

          
val

      

      
Gets or sets the selection. If the value parameter is not specified, the id attribute of the currently selected element is returned. If the value parameter is specified it will become the current selection.

      

          

              ParameterTypeDescription
          

          
value (optional)object

              

                    

                        Single-ValuedMulti-Valued
                    

                    

                        Attached to select
                        Value of the value attribute of the option that should be selected
                        Array of values specified to the left. null for empty.
                    

                  

                      Attached to input[type=hidden]
                      An object representing the selection. Should at least contain an id key. The rest of the keys should be determined by the custom rendering function, the default rendering function only needs an additional text key
                      Array of objects specified to the left. null for empty.
                  


              



          

      

      Example: 
alert("Selected value is: "+$("#e8").select2("val")); $("#e8").select2("val", {id:"CA", text:"Califoria"});


      

          
Events

      


      

          

              
change

              
Fired when selection is changed.

              
This event is not fired when the selection is changed using Select2's val() method.

          

      

      

      

        

      

           
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