select2 - how to allow a null value

To specify a null value you set the Select2 value to null and the placeholder will appear.

$('select').select2({
    placeholder: 'Your NULL value caption',
    allowClear: true   // Shows an X to allow the user to clear the value.
});

There are/were ways (via a custom data adapter or previous versions) to create a null value entry that users could select. I know because that is what I previously did but that has now changed.

Select2 4.0.3: See: https://select2.org/selections

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IMPORTANT EDIT: As of Version 4.0.4 (yesterday) there is a fix that allows selecting options with blank or 0 option values. See: https://github.com/select2/select2/releases/tag/4.0.4

To enable this you need to add your NULL value and remove the "placeholder" and the "allowClear" options.

If you don't remove the "placeholder" option it will hide your "NULL" entry.

If you leave the "allowClear" then clicking the "X" will cause an error.

It can be done via HTML element attributes (for select2)

<select ... data-allow-clear=true >