{!REQUIRESCRIPT("/soap/ajax/32.0/connection.js")}

var result = sforce.connection.query("SELECT Id FROM PermissionSetAssignment WHERE PermissionSet.Name = 'Sample_Permission_Set' AND AssigneeId = '{!$User.Id}'");
var psAssignment = result.getArray("records");

if (psAssignment.length === 1) {
    //Write your logic
} else {
    alert('You don't have access to this feature.');
}