使用 AJAX 时如何设置 Select2的初始值？

小开

最佳答案

You are doing most things correctly, it looks like the only problem you are hitting is that you are not triggering the change method after you are setting the new value. Without a change event, Select2 cannot know that the underlying value has changed so it will only display the placeholder. Changing your last part to

.val(initial_creditor_id).trigger('change');

Should fix your issue, and you should see the UI update right away.

This is assuming that you have an <option> already that has a value of initial_creditor_id. If you do not Select2, and the browser, will not actually be able to change the value, as there is no option to switch to, and Select2 will not detect the new value. I noticed that your <select> only contains a single option, the one for the placeholder, which means that you will need to create the new <option> manually.

var $option = $("<option selected></option>").val(initial_creditor_id).text("Whatever Select2 should display");

And then append it to the <select> that you initialized Select2 on. You may need to get the text from an external source, which is where initSelection used to come into play, which is still possible with Select2 4.0.0. Like a standard select, this means you are going to have to make the AJAX request to retrieve the value and then set the <option> text on the fly to adjust.

var $select = $('.creditor_select2');


$select.select2(/* ... */); // initialize Select2 and any events


var $option = $('<option selected>Loading...</option>').val(initial_creditor_id);


$select.append($option).trigger('change'); // append the option and update Select2


$.ajax({ // make the request for the selected data object
type: 'GET',
url: '/api/for/single/creditor/' + initial_creditor_id,
dataType: 'json'
}).then(function (data) {
// Here we should have the data object
$option.text(data.text).val(data.id); // update the text that is displayed (and maybe even the value)
$option.removeData(); // remove any caching data that might be associated
$select.trigger('change'); // notify JavaScript components of possible changes
});

While this may look like a lot of code, this is exactly how you would do it for non-Select2 select boxes to ensure that all changes were made.

小开

Hi was almost quitting this and go back to select 3.5.1. But finally I got the answer!

$('#test').select2({
placeholder: "Select a Country",
minimumResultsForSearch: 2,
ajax: {
url: '...',
dataType: 'json',
cache: false,
data: function (params) {
var queryParameters = {
q: params.term
}
return queryParameters;
},
processResults: function (data) {
return {
results: data.items
};
}
}
});


var option1 = new Option("new",true, true);


$('#status').append(option1);


$('#status').trigger('change');

Just be sure that the new option is one of the select2 options. I get this by a json.

小开

The issue of being forced to trigger('change') drove me nuts, as I had custom code in the change trigger, which should only trigger when the user changes the option in the dropdown. IMO, change should not be triggered when setting an init value at the start.

I dug deep and found the following: https://github.com/select2/select2/issues/3620

Example:

$dropDown.val(1).trigger('change.select2');

小开

What I've done is more clean and needs to make two arrays :

one contains a list of Object with id and a text (in my case its id and name, depending of your templateResult) (its what you get from ajax query)
the second is only an array of ids (selection value)

I initialize select2 using the first array as data, and the second as the val.

An example function with as parameters a dict of id:name.

function initMyList(values) {
var selected = [];
var initials = [];


for (var s in values) {
initials.push({id: s, name: values[s].name});
selected.push(s);
}


$('#myselect2').select2({
data: initials,
ajax: {
url: "/path/to/value/",
dataType: 'json',
delay: 250,
data: function (params) {
return {
term: params.term,
page: params.page || 1,
};
},
processResults: function (data, params) {
params.page = params.page || 1;


return {
results: data.items,
pagination: {
more: (params.page * 30) < data.total_count
}
};
},
cache: true
},
minimumInputLength: 1,
tokenSeparators: [",", " "],
placeholder: "Select none, one or many values",
templateResult: function (item) { return item.name; },
templateSelection: function (item) { return item.name; },
matcher: function(term, text) { return text.name.toUpperCase().indexOf(term.toUpperCase()) != -1; },
});


$('#myselect2').val(selected).trigger('change');
}

You can feed the initials value using ajax calls, and use jquery promises to do the select2 initialization.

小开

I am adding this answer mainly because I can't comment above! I found it was the comment by @Nicki and her jsfiddle, https://jsfiddle.net/57co6c95/, that eventually got this working for me.

Among other things, it gave examples of the format for the json needed. The only change I had to make was that my initial results were returned in the same format as the other ajax call so I had to use

$option.text(data[0].text).val(data[0].id);

rather than

$option.text(data.text).val(data.id);

小开

One scenario that I haven't seen people really answer, is how to have a preselection when the options are AJAX sourced, and you can select multiple. Since this is the go-to page for AJAX preselection, I'll add my solution here.

$('#mySelect').select2({
ajax: {
url: endpoint,
dataType: 'json',
data: [
{ // Each of these gets processed by fnRenderResults.
id: usersId,
text: usersFullName,
full_name: usersFullName,
email: usersEmail,
image_url: usersImageUrl,
selected: true // Causes the selection to actually get selected.
}
],
processResults: function(data) {


return {
results: data.users,
pagination: {
more: data.next !== null
}
};


}
},
templateResult: fnRenderResults,
templateSelection: fnRenderSelection, // Renders the result with my own style
selectOnClose: true
});

小开

after spending a few hours searching for a solution, I decided to create my own. He it is:

 function CustomInitSelect2(element, options) {
if (options.url) {
$.ajax({
type: 'GET',
url: options.url,
dataType: 'json'
}).then(function (data) {
element.select2({
data: data
});
if (options.initialValue) {
element.val(options.initialValue).trigger('change');
}
});
}
}

And you can initialize the selects using this function:

$('.select2').each(function (index, element) {
var item = $(element);
if (item.data('url')) {
CustomInitSelect2(item, {
url: item.data('url'),
initialValue: item.data('value')
});
}
else {
item.select2();
}
});

And of course, here is the html:

<select class="form-control select2" id="test1" data-url="mysite/load" data-value="123"></select>

小开

Create simple ajax combo with de initial seleted value for select2 4.0.3

<select name="mycombo" id="mycombo""></select>
<script>
document.addEventListener("DOMContentLoaded", function (event) {
selectMaker.create('table', 'idname', '1', $("#mycombo"), 2, 'type');
});
</script>

library .js

var selectMaker = {
create: function (table, fieldname, initialSelected, input, minimumInputLength = 3, type ='',placeholder = 'Select a element') {
if (input.data('select2')) {
input.select2("destroy");
}
input.select2({
placeholder: placeholder,
width: '100%',
minimumInputLength: minimumInputLength,
containerCssClass: type,
dropdownCssClass: type,
ajax: {
url: 'ajaxValues.php?getQuery=true&table=' + table + '&fieldname=' + fieldname + '&type=' + type,
type: 'post',
dataType: 'json',
contentType: "application/json",
delay: 250,
data: function (params) {
return {
term: params.term, // search term
page: params.page
};
},
processResults: function (data) {
return {
results: $.map(data.items, function (item) {
return {
text: item.name,
id: item.id
}
})
};
}
}
});
if (initialSelected>0) {
var $option = $('<option selected>Cargando...</option>').val(0);
input.append($option).trigger('change'); // append the option and update Select2
$.ajax({// make the request for the selected data object
type: 'GET',
url: 'ajaxValues.php?getQuery=true&table=' + table + '&fieldname=' + fieldname + '&type=' + type + '&initialSelected=' + initialSelected,
dataType: 'json'
}).then(function (data) {
// Here we should have the data object
$option.text(data.items[0].name).val(data.items[0].id); // update the text that is displayed (and maybe even the value)
$option.removeData(); // remove any caching data that might be associated
input.trigger('change'); // notify JavaScript components of possible changes
});
}
}
};

and the php server side

<?php
if (isset($_GET['getQuery']) && isset($_GET['table']) && isset($_GET['fieldname'])) {
//parametros carga de petición
parse_str(file_get_contents("php://input"), $data);
$data = (object) $data;
if (isset($data->term)) {
$term = pSQL($data->term);
}else{
$term = '';
}
if (isset($_GET['initialSelected'])){
$id =pSQL($_GET['initialSelected']);
}else{
$id = '';
}
if ($_GET['table'] == 'mytable' && $_GET['fieldname'] == 'mycolname' && $_GET['type'] == 'mytype') {


if (empty($id)){
$where = "and name like '%" . $term . "%'";
}else{
$where = "and id= ".$id;
}


$rows = yourarrayfunctionfromsql("SELECT id, name
FROM yourtable
WHERE 1 " . $where . "
ORDER BY name ");
}


$items = array("items" => $rows);
$var = json_encode($items);
echo $var;
?>

小开

If you are using a templateSelection and ajax, some of these other answers may not work. It seems that creating a new option element and setting the value and text will not satisfy the template method when your data objects use other values than id and text.

Here is what worked for me:

$("#selectElem").select2({
ajax: { ... },
data: [YOUR_DEFAULT_OBJECT],
templateSelection: yourCustomTemplate
}

Check out the jsFiddle here: https://jsfiddle.net/shanabus/f8h1xnv4

In my case, I had to processResults in since my data did not contain the required id and text fields. If you need to do this, you will also need to run your initial selection through the same function. Like so:

$(".js-select2").select2({
ajax: {
url: SOME_URL,
processResults: processData
},
data: processData([YOUR_INIT_OBJECT]).results,
minimumInputLength: 1,
templateSelection: myCustomTemplate
});


function processData(data) {
var mapdata = $.map(data, function (obj) {
obj.id = obj.Id;
obj.text = '[' + obj.Code + '] ' + obj.Description;
return obj;
});
return { results: mapdata };
}


function myCustomTemplate(item) {
return '<strong>' + item.Code + '</strong> - ' + item.Description;
}

小开

For a simple and semantic solution i prefer to define the initial value in HTML, example:

<select name="myfield" data-placeholder="Select an option">
<option value="initial-value" selected>Initial text</option>
</select>

So when i call $('select').select2({ ajax: {...}}); the initial value is initial-value and its option text is Initial text.

My current Select2 version is 4.0.3, but i think it has a great compatibility with other versions.

小开

It's works for me ...

Don't use jQuery, only HTML: Create the option value you will display as selected. If ID it's in select2 data it will selected automatically.

<select id="select2" name="mySelect2">
<option value="mySelectedValue">
Hello, I'm here!
</option>
</select>

Select2.org - Default Pre Selected values

小开

https://github.com/select2/select2/issues/4272 only this solved my problem. even you set default value by option, you have to format the object, which has the text attribute and this is what you want to show in your option. so, your format function have to use || to choose the attribute which is not empty.

小开

This is the solution that worked for me for multiple + template :

(my ajax return an additional parameter, "email")

// my template
var my_template_func = function (data){
if( data.email )
var email = data.email;
else if( data.element )
var email = data.element.dataset.email;
var html = '<span><span>'+data.text+'</span> - <em>'+email+'</em></span>';
return $(html);
};


// select2 init
$('.my-select').select2({
ajax: {
url: '...',
dataType: 'json',
},
templateResult: my_template_func,
templateSelection: my_template_func,
});

Then either i set default option(s) in html

<option value="555" data-email="test@exemple.com" selected>Bob</option>

Or i add the option(s) with JS

// add option(s)
var option = new Option('Bob', 555, true, true);
option.dataset.email = 'test@exemple.com';
$('.my-select').append(option).trigger('change');