Javascript: How can I filter some dataflow results?

Example:
```
var a = request.body;
var obj = {
"body": a.a;
"headers": a.b
}
foo(obj)
```
while I query the above code, there are two flow path:
```
1. a -> obj.body -> foo
2. a -> obj.headers -> foo
```
And I would like to show result 1 only, and filter result 2.
How can I solve the problem? Thanks