selectAllButton

defines whether the Select All button should be shown

selectAllButton?: boolean;

Example

var combo = new dhx.Combobox("combo_container", {    // enables multiple selection of options    multiselection:true,    // shows the Select All button    selectAllButton: true});

Related sample: Combobox. Select All Button

note

To be able to select several options you need to enable the multiselection option.