fires before the task selection state is being changed (the task is being selected or unselected)

void onBeforeTaskMultiSelect(string|number id,boolean state,Event|null e);
idstring|numberthe id of a task
statebooleantrue if the task is going to be selected, false - if unselected
eEvent|nulla native event object


gantt.attachEvent("onBeforeTaskMultiSelect", function(id, state, e){
    // some logic here
     return true;


This event is defined in the multiselect extension, so you need to activate the multiselect plugin. Read the details in the Multi-Task Selection article.

The event is called for each task of the range.

The event is blockable, returning false will cancel the change of the task selection state.

See also
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