Trigger Event On Deletion Of Grid Row

To trigger an event when a row from a Child Table has been deleted (when user clicks on delete button), you need to add a handler the fieldname_remove event to Child Table, where fieldname is the fieldname of the Child Table in Parent Table declaration.

For example:

Assuming that your parent DocType is named Item has a Table Field linked to Item Color DocType with decloration name color.

In order to "catch" the delete event:

frappe.ui.form.on('Item Color', {
 color_remove: function(frm) {
 // You code here
 // If you console.log(frm.doc.color) you will get the remaining color list
 }
);

The same process is used to trigger the add event (when user clicks on add row button):

frappe.ui.form.on('Item Color', {
 color_remove: function(frm) {
 // You code here
 // If you console.log(frm.doc.color) you will get the remaining color list
 },
 color_add: function(frm) {}
});

Notice that the handling is be made on Child DocType Table form.ui.on and not on Parent Doctype so a minimal full example is:

frappe.ui.form.on('Item',{
 // Your client side handling for Item
});

frappe.ui.form.on('Item Color', {
 color_remove: function(frm) {
 // Deleting is triggered here
 }
);

Handlers are:

1. fieldname_add
2. fieldname_move
3. fieldname_before_remove
4. fieldname_remove