Why does javascript-angular jump to the upper-and lower-level to the upper-level?

1. the col data table contains three fields: name, id, and id. As follows: horizontal bars (s) indicate the subitem of a data item. {Code...} If I retrieve a subitem through the parent id, I do not know how to return the subitem to the parent project. The general idea is that, through the... 1 in a, there is a col data table, which contains three fields: name, id, and id.
As follows: horizontal bars (s) indicate the subitem of a data item.

{'A', '3', '2'} {'a-s', '4', '3'} {'a-s', '5 ', '3'} {'a-s-s', '6', '5'} {'a-s-s', '7 ', '4'} {'B', '8', '2 '}

Now, if I retrieve a subitem using the parent id, I do not know how to return the subitem to the parent project.
The general idea is that I obtained a string of son data (such as 'A-s') through id (3) in ). The parent id (3) is recorded in the data corresponding to son ). I use this parent id (3) to find the pid (2) with id = 3 in the database, and then return son data with parent id 2 (a and B ).
But I don't know how, as if there are too many layers, it will be messy.

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1. the col data table contains three fields: name, id, and id.
As follows: horizontal bars (s) indicate the subitem of a data item.

{'A', '3', '2'} {'a-s', '4', '3'} {'a-s', '5 ', '3'} {'a-s-s', '6', '5'} {'a-s-s', '7 ', '4'} {'B', '8', '2 '}

Now, if I retrieve a subitem using the parent id, I do not know how to return the subitem to the parent project.
The general idea is that I obtained a string of son data (such as 'A-s') through id (3) in ). The parent id (3) is recorded in the data corresponding to son ). I use this parent id (3) to find the pid (2) with id = 3 in the database, and then return son data with parent id 2 (a and B ).
But I don't know how, as if there are too many layers, it will be messy.