This feature has been removed from the Web standards. Though some browsers may still support it, it is in the process of being dropped. Avoid using it and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
dialogArguments property returns the parameters that were passed into the
window.showModalDialog() method. This lets you determine what parameters were specified when the modal dialog was created.
value = window.dialogArguments;