288 lines
9.9 KiB
Markdown
288 lines
9.9 KiB
Markdown
---
|
|
title: Ajax (remote data)
|
|
metadata:
|
|
description: Select2 provides extensive support for populating dropdown items from a remote data source.
|
|
taxonomy:
|
|
category: docs
|
|
process:
|
|
twig: true
|
|
never_cache_twig: true
|
|
---
|
|
|
|
Select2 comes with AJAX support built in, using jQuery's AJAX methods. In this example, we can search for repositories using GitHub's API:
|
|
|
|
<select class="js-example-data-ajax form-control"></select>
|
|
|
|
**In your HTML:**
|
|
|
|
```
|
|
<select class="js-data-example-ajax"></select>
|
|
```
|
|
|
|
**In your Javascript:**
|
|
|
|
```
|
|
$('.js-example-data-ajax').select2({
|
|
ajax: {
|
|
url: 'https://api.github.com/search/repositories',
|
|
dataType: 'json'
|
|
// Additional AJAX parameters go here; see the end of this chapter for the full code of this example
|
|
}
|
|
});
|
|
```
|
|
|
|
You can configure how Select2 searches for remote data using the `ajax` option. Select2 will pass any options in the `ajax` object to jQuery's `$.ajax` function, or the `transport` function you specify.
|
|
|
|
>>> For **remote data sources only**, Select2 does not create a new `<option>` element until the item has been selected for the first time. This is done for performance reasons. Once an `<option>` has been created, it will remain in the DOM even if the selection is later changed.
|
|
|
|
## Request parameters
|
|
|
|
Select2 will issue a request to the specified URL when the user opens the control (unless there is a `minimumInputLength` set), and again every time the user types in the search box. By default, it will send the following as query string parameters:
|
|
|
|
- `term` : The current search term in the search box.
|
|
- `q` : Contains the same contents as `term`.
|
|
- `_type`: A "request type". Will usually be `query`, but changes to `query_append` for paginated requests.
|
|
- `page` : The current page number to request. Only sent for paginated (infinite scrolling) searches.
|
|
|
|
For example, Select2 might issue a request that looks like: `https://api.github.com/search/repositories?term=sel&_type=query&q=sel`.
|
|
|
|
Sometimes, you may need to add additional query parameters to the request. You can modify the parameters that are sent with the request by overriding the `ajax.data` option:
|
|
|
|
```
|
|
$('#mySelect2').select2({
|
|
ajax: {
|
|
url: 'https://api.github.com/search/repositories',
|
|
data: function (params) {
|
|
var query = {
|
|
search: params.term,
|
|
page: params.page
|
|
}
|
|
|
|
// Query parameters will be ?search=[term]&page=[page]
|
|
return query;
|
|
}
|
|
}
|
|
});
|
|
```
|
|
|
|
## Transforming response data
|
|
|
|
You can use the `ajax.processResults` option to transform the data returned by your API into the format expected by Select2:
|
|
|
|
```
|
|
$('#mySelect2').select2({
|
|
ajax: {
|
|
url: '/example/api',
|
|
processResults: function (data) {
|
|
// Tranforms the top-level key of the response object from 'items' to 'results'
|
|
return {
|
|
results: data.items
|
|
};
|
|
}
|
|
}
|
|
});
|
|
```
|
|
|
|
>>> Select2 expects results from the remote endpoint to be filtered on the **server side**. If server-side filtering is not possible, you may be interested in using Select2's [support for data arrays](/data-sources/arrays) instead.
|
|
|
|
## Default (pre-selected) values
|
|
|
|
You may wish to set a pre-selected default value for a Select2 control that receives its data from an AJAX request.
|
|
|
|
To provide default selections, you may include an `<option>` for each selection that contains the value and text that should be displayed:
|
|
|
|
```
|
|
<select class="js-example-data-ajax form-control">
|
|
<option value="3620194" selected="selected">select2/select2</option>
|
|
</select>
|
|
```
|
|
|
|
To achieve this programmatically, you will need to [create and append a new `Option`](/programmatic-control/add-select-clear-items).
|
|
|
|
## Rate-limiting requests
|
|
|
|
You can tell Select2 to wait until the user has finished typing their search term before triggering the AJAX request. Simply use the `ajax.delay` configuration option to tell Select2 how long to wait after a user has stopped typing before sending the request:
|
|
|
|
```
|
|
$('#mySelect2').select2({
|
|
ajax: {
|
|
delay: 250 // wait 250 milliseconds before triggering the request
|
|
}
|
|
});
|
|
```
|
|
|
|
## Dynamic URLs
|
|
|
|
If there isn't a single url for your search results, or you need to call a function to determine the url to use, you can specify a callback for the `ajax.url` option to generate the url. The current search query will be passed in through the `params` option:
|
|
|
|
```
|
|
$('#mySelect2').select2({
|
|
ajax: {
|
|
url: function (params) {
|
|
return '/some/url/' + params.term;
|
|
}
|
|
}
|
|
});
|
|
```
|
|
|
|
## Alternative transport methods
|
|
|
|
Select2 uses the transport method defined in `ajax.transport` to send requests to your API. By default this transport method is `jQuery.ajax`, but it can be easily overridden:
|
|
|
|
```
|
|
$('#mySelect2').select2({
|
|
ajax: {
|
|
transport: function (params, success, failure) {
|
|
var request = new AjaxRequest(params.url, params);
|
|
request.on('success', success);
|
|
request.on('failure', failure);
|
|
}
|
|
}
|
|
});
|
|
```
|
|
|
|
## jQuery `$.ajax` options
|
|
|
|
All options passed to `ajax` will be directly passed to the `$.ajax` function that executes AJAX requests.
|
|
|
|
There are a few custom options that Select2 will intercept, allowing you to customize the request as it is being made:
|
|
|
|
```
|
|
ajax: {
|
|
// The number of milliseconds to wait for the user to stop typing before
|
|
// issuing the ajax request.
|
|
delay: 250,
|
|
// You can craft a custom url based on the parameters that are passed into the
|
|
// request. This is useful if you are using a framework which has
|
|
// JavaScript-based functions for generating the urls to make requests to.
|
|
//
|
|
// @param params The object containing the parameters used to generate the
|
|
// request.
|
|
// @returns The url that the request should be made to.
|
|
url: function (params) {
|
|
return UrlGenerator.Random();
|
|
},
|
|
// You can pass custom data into the request based on the parameters used to
|
|
// make the request. For `GET` requests, the default method, these are the
|
|
// query parameters that are appended to the url. For `POST` requests, this
|
|
// is the form data that will be passed into the request. For other requests,
|
|
// the data returned from here should be customized based on what jQuery and
|
|
// your server are expecting.
|
|
//
|
|
// @param params The object containing the parameters used to generate the
|
|
// request.
|
|
// @returns Data to be directly passed into the request.
|
|
data: function (params) {
|
|
var queryParameters = {
|
|
q: params.term
|
|
}
|
|
|
|
return queryParameters;
|
|
},
|
|
// You can modify the results that are returned from the server, allowing you
|
|
// to make last-minute changes to the data, or find the correct part of the
|
|
// response to pass to Select2. Keep in mind that results should be passed as
|
|
// an array of objects.
|
|
//
|
|
// @param data The data as it is returned directly by jQuery.
|
|
// @returns An object containing the results data as well as any required
|
|
// metadata that is used by plugins. The object should contain an array of
|
|
// data objects as the `results` key.
|
|
processResults: function (data) {
|
|
return {
|
|
results: data
|
|
};
|
|
},
|
|
// You can use a custom AJAX transport function if you do not want to use the
|
|
// default one provided by jQuery.
|
|
//
|
|
// @param params The object containing the parameters used to generate the
|
|
// request.
|
|
// @param success A callback function that takes `data`, the results from the
|
|
// request.
|
|
// @param failure A callback function that indicates that the request could
|
|
// not be completed.
|
|
// @returns An object that has an `abort` function that can be called to abort
|
|
// the request if needed.
|
|
transport: function (params, success, failure) {
|
|
var $request = $.ajax(params);
|
|
|
|
$request.then(success);
|
|
$request.fail(failure);
|
|
|
|
return $request;
|
|
}
|
|
}
|
|
```
|
|
|
|
## Additional examples
|
|
|
|
This code powers the Github example presented at the beginning of this chapter:
|
|
|
|
<pre data-fill-from=".js-code-placeholder"></pre>
|
|
|
|
<script type="text/javascript" class="js-code-placeholder">
|
|
|
|
$(".js-example-data-ajax").select2({
|
|
ajax: {
|
|
url: "https://api.github.com/search/repositories",
|
|
dataType: 'json',
|
|
delay: 250,
|
|
data: function (params) {
|
|
return {
|
|
q: params.term, // search term
|
|
page: params.page
|
|
};
|
|
},
|
|
processResults: function (data, params) {
|
|
// parse the results into the format expected by Select2
|
|
// since we are using custom formatting functions we do not need to
|
|
// alter the remote JSON data, except to indicate that infinite
|
|
// scrolling can be used
|
|
params.page = params.page || 1;
|
|
|
|
return {
|
|
results: data.items,
|
|
pagination: {
|
|
more: (params.page * 30) < data.total_count
|
|
}
|
|
};
|
|
},
|
|
cache: true
|
|
},
|
|
placeholder: 'Search for a repository',
|
|
escapeMarkup: function (markup) { return markup; }, // let our custom formatter work
|
|
minimumInputLength: 1,
|
|
templateResult: formatRepo,
|
|
templateSelection: formatRepoSelection
|
|
});
|
|
|
|
function formatRepo (repo) {
|
|
if (repo.loading) {
|
|
return repo.text;
|
|
}
|
|
|
|
var markup = "<div class='select2-result-repository clearfix'>" +
|
|
"<div class='select2-result-repository__avatar'><img src='" + repo.owner.avatar_url + "' /></div>" +
|
|
"<div class='select2-result-repository__meta'>" +
|
|
"<div class='select2-result-repository__title'>" + repo.full_name + "</div>";
|
|
|
|
if (repo.description) {
|
|
markup += "<div class='select2-result-repository__description'>" + repo.description + "</div>";
|
|
}
|
|
|
|
markup += "<div class='select2-result-repository__statistics'>" +
|
|
"<div class='select2-result-repository__forks'><i class='fa fa-flash'></i> " + repo.forks_count + " Forks</div>" +
|
|
"<div class='select2-result-repository__stargazers'><i class='fa fa-star'></i> " + repo.stargazers_count + " Stars</div>" +
|
|
"<div class='select2-result-repository__watchers'><i class='fa fa-eye'></i> " + repo.watchers_count + " Watchers</div>" +
|
|
"</div>" +
|
|
"</div></div>";
|
|
|
|
return markup;
|
|
}
|
|
|
|
function formatRepoSelection (repo) {
|
|
return repo.full_name || repo.text;
|
|
}
|
|
</script>
|