Example: Adding flow through 'decodeURIComponent'

In this example, we'll show how to add flow through calls to `decodeURIComponent`:

.. code-block:: js

This flow is already recognized by the CodeQL JS analysis, but this is how it could be added with an extension:

.. code-block:: yaml

To break this down:

- Since we're adding flow *through* a function call, we add a tuple to the **summaryModel** extension point.

- The first column, **"global"**, begins the search for relevant calls at references to the global object.

In JavaScript, global variables are properties of the global object, so this lets us access global variables or functions.

- The second column, **Member[decodeURIComponent]**, is a path leading to the function calls we wish to model.

In this case, we select references to the **decodeURIComponent** member from the global object, that is,

the global variable named **decodeURIComponent**.

- The third column, **Argument[0]**, indicates the input of the flow. In this case, the first argument to the function call.

- The fourth column, **ReturnValue**, indicates the output of the flow. In this case, the return value of the function call.

- The last column, **taint**, indicates the kind of flow to add. The value **taint** means the output is not necessarily equal

to the input, but was was derived from the input in a taint-preserving way.