Example for automatic detection with class .field-select and data attributes

<select class="field-select" data-sorting="asc" 
    data-placeholder="Your selection" 
    data-no-results="No results found">
    <option value=""></option>    
    <option value="5">Option 5</option>
    <option value="1">Option 1</option>    
    <option value="3" selected>Option 3</option>
    <option value="2">Option 2</option>
    <option value="4">Option 4</option>
</select>

Example for automatic detection with class .field-select and data attributes

<select class="field-select" data-sorting="desc" 
    data-placeholder="Your items" 
    data-no-results="No results found" 
    data-all-selected="All items selected" multiple>
    <option value="1">Option 1</option>
    <option value="2" selected>Option 2</option>
    <option value="3">Option 3</option>
    <option value="4">Option 4</option>
    <option value="5" selected>Option 5</option>
</select>

Initialization with plugin, callback and multiple date attributes for options

let select = $('[name="select[]"]').select({
    onChange: function(options) {
        console.log(options);
    }
    onDelete: function(options) {
        console.log(options);
    }    
});

select.each(function() {
    this.clear(); // Optional method
    this.values([2, 1]);
});

Add class to select.tag-secondary and optional opacity with .tag- and value from 10 to 90 (%)

Add attribute required, if use form to post data

<select class="field-select" name="options[]" multiple required>
    <option value="1">Option 1</option>
    <option value="2">Option 2</option>
    <option value="3">Option 3</option>
    <option value="4">Option 4</option>
    <option value="5">Option 5</option>
</select>

Add attribute data to select data-readonly with value

<select class="field-select" multiple data-readonly="true">
    <option value="1">Option 1</option>
    <option value="2" selected>Option 2</option>
    <option value="3">Option 3</option>
    <option value="4" selected>Option 4</option>
    <option value="5">Option 5</option>
</select>

Add buttons with name for select field and suffix -all and -none

<select class="field-select" name="items[]" multiple>
    ...
</select>

<input id="items-all" type="button" class="btn btn-success" value="All select" />
<input id="items-none" type="button" class="btn btn-danger" value="None" />

Add data-selected attribute with string values [2,4,3] to keep selection order

<select class="field-select" data-selected="[2,4,3]" multiple>
    <option value="1">Option 1</option>
    <option value="2">Option 2</option>
    <option value="3">Option 3</option>
    ...
</select>