Two functions, listed here, provide JavaScript Function objects reflecting MySQL stored routines:

Use the close() method to close the resource associated with the stored routine. An error is thrown if the routine, after it is closed, is called again, or if its close() method is called again.

The following example creates two stored functions getArea() and getDiag(), then creates and runs a JavaScript stored procedure procRect which uses these functions by instantiating them and executing them by means of Function objects.

mysql> CREATE FUNCTION getArea(w INT, h INT)
    -> RETURNS INT DETERMINISTIC
    -> RETURN w * h;
Query OK, 0 rows affected (0.01 sec)

mysql> CREATE FUNCTION getDiag(w INT, h INT) 
    ->   RETURNS FLOAT DETERMINISTIC
    ->   RETURN Math.sqrt(Math.pow(w, 2) + Math.pow(h, 2));
Query OK, 0 rows affected (0.01 sec)

mysql> CREATE PROCEDURE procRect(IN x INT, IN y INT) LANGUAGE JAVASCRIPT
    -> AS $$
    $>   console.clear()
    $> 
    $>   let s = session.getDefaultSchema()
    $>   let f = s.getFunction("getArea")
    $>   let g = s.getFunction("getDiag")
    $> 
    $>   let a = x
    $>   let b = y
    $> 
    $>   console.log (
    $>                 "Width: " + a + ", Height: " + b + "; Area: " + 
    $>                 f(a,b) + "; Diagonal: " + g(a,b)
    $>               )
    $> 
    $>   f.close()
    $>   g.close()
    $> $$;
Query OK, 0 rows affected (0.01 sec)

mysql> CALL procRect(5, 10);
Query OK, 0 rows affected (0.03 sec)

mysql> SELECT mle_session_state("stdout")\G
*************************** 1. row ***************************
mle_session_state("stdout"): Width: 5, Height: 10; Area: 50; Diagonal: 11.180339813232422

1 row in set (0.00 sec)

mysql> CALL procRect(2, 25);
Query OK, 0 rows affected (0.02 sec)

mysql> SELECT mle_session_state("stdout")\G
*************************** 1. row ***************************
mle_session_state("stdout"): Width: 2, Height: 25; Area: 50; Diagonal: 25.079872131347656

1 row in set (0.00 sec)

For stored functions, arguments are simply passed by value, as shown in the examples just shown with getDiag() and getArea(). For stored procedures, argument handling is as follows:

mysql.arg().  This function is always called as a method of the global mysql object. It creates an Argument object, which can be assigned a value on creation, or by a procedure call. Afterwards, the value can be retrieved as argument.val. This is shown in the following example, where argument instances a and b are created in use_my_proc() to act as placeholders for y and z in my_proc():

mysql> CREATE PROCEDURE my_proc(
    ->   IN x INT,
    ->   OUT y VARCHAR(20),
    ->   INOUT z TEXT
    -> )
    -> LANGUAGE JAVASCRIPT
    -> AS $$
    $>     y = "Hello world " + x
    $>     z += "Hello again JS"
    $> $$;
Query OK, 0 rows affected (0.04 sec)

mysql> CREATE PROCEDURE use_my_proc() LANGUAGE JAVASCRIPT
    -> AS $$
    $>     console.clear()
    $>
    $>     let s = session.getDefaultSchema()
    $>     let p = s.getProcedure("my_proc")
    $>
    $>     let a = mysql.arg()
    $>     let b = mysql.arg("World ")
    $>
    $>     p(42, a, b)
    $>
    $>     console.log(a.val)
    $>     console.log(b.val)
    $>
    $>     p.close()
    $> $$;
Query OK, 0 rows affected (0.01 sec)

mysql> CALL use_my_proc();
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT mle_session_state("stdout")\G
*************************** 1. row ***************************
mle_session_state("stdout"): Hello world 42
World Hello again JS

1 row in set (0.00 sec)

Equivalents between the MySQL types of OUT or INOUT parameters and JavaScript types are shown in the following table: