Problem with sintax of selectpicker('refresh')

问题

I try to populate a select form with data from a json file.

[{"matricola":"1", "nome":"aaaaa"},{"matricola":"2", "nome":"bbbbbb"}]

If I use select it works, if i try to use selectpicker I do not understand where I have to refresh the selectpicker in my javascript code.

Here my code:

<div class="form-group  ">
<select id="cf" class="selectpicker show-tick form-control" data-dropup-auto="false" data-live-search="true" required="" name="cf">
</select>
</div> 

<script>            
let dropdown = document.getElementById('cf');
dropdown.length = 0;

let defaultOption = document.createElement('option');
defaultOption.text = 'Seleziona un dipendente';

dropdown.add(defaultOption);
dropdown.selectedIndex = 0;

const url = 'tables/griglia_dipendenti_incarichi.php';

const request = new XMLHttpRequest();
request.open('GET', url, true);

request.onload = function() {
  if (request.status === 200) {
    const data = JSON.parse(request.responseText);
    let option;
    for (let i = 0; i < data.length; i++) {
      option = document.createElement('option');
      option.text = data[i].nome;
      option.value = data[i].matricola;
      if (i==0){
        alert(option.text);
      }
      dropdown.add(option);
    }
   } else {
    // Reached the server, but it returned an error
  }   
}

request.onerror = function() {
  console.error('An error occurred fetching the JSON from ' + url);
};

request.send();
</script> 

I have tried with

dropdown.add(option).selectpicker('refresh');

but it do no works

回答1:

Firstly you should read this guide - https://developer.snapappointments.com/bootstrap-select/ and check if you have linked all needed files to the page.

Next thing is to initialize Bootstrap-select plugin. You can do it for all select tags on the page:

$('select').selectpicker();

or just for your element:

$('#cf').selectpicker();

Now, if you change any select and want a user to see changes, you need to refresh selectpicker plugin.
If you use a new version of Bootstrap-select plugin, then try this:

$('#cf').selectpicker('refresh');

Otherwise use this:

$('#cf').selectpicker('destroy');
$('#cf').selectpicker();  

p.s.: here's a simple exapmle - https://jsfiddle.net/Denisdude/pf7qreum/17/

回答2:

Many thanks. It works with fake data not with a online json

Here my javascript code:

<script>
$('#cf').selectpicker();
var Request = function () {

    let dropdown = document.getElementById('cf');
    dropdown.length = 0;

    let defaultOption = document.createElement('option');
    defaultOption.text = 'Seleziona un dipendente';

    dropdown.add(defaultOption);
    dropdown.selectedIndex = 0;

    // data
    const url = 'tables/griglia_dipendenti_incarichi.php';

    const request = new XMLHttpRequest();
    request.open('GET', url, true);

    request.onload = function() {
      if (request.status === 200) {
        const data = JSON.parse(request.responseText);
        for (let i = 0; i < data.length; i++) {
            let option;
            option = document.createElement('option');
            option.text = data[i].nome;
            option.value = data[i].matricola;
            /*if (i==0){
                alert(option.text);
            }*/
            dropdown.add(option);
        }

       } else {
        // Reached the server, but it returned an error
      }   
    }

    request.onerror = function() {
      console.error('An error occurred fetching the JSON from ' + url);
    };

    request.send();

    //alert('request has been sent!');

    // here we refresh selectpicker plugin
    //$('#cf').selectpicker('refresh');
    // OR destroy and initialize it IF "refresh" didn't work
    $('#cf').selectpicker('destroy');
    $('#cf').selectpicker();    

};

Request();

</script>

where is my last error?

来源：https://stackoverflow.com/questions/58248613/problem-with-sintax-of-selectpickerrefresh