called when filtering process is started, but data is not filtered yet
id | id | the column id |
value | id | the value to be fitlered by |
config | object | the filter configuration |
boolean | returning false will prevent data filtering |
dtable.attachEvent("onBeforeFilter", function(id, value, config){
//ignores short filter-strings during filtering
if (value.length < 3) return false;
})