Context expressions

Literal

Creates a new context with the given entries. Each entry has a key and a value. The key is either a name or a string. The value can be any type.

Refer to the naming conventions for valid key names.

{
  a: 1,
  b: 2
}
// {a:1, b:2}

{
  "a": 1,
  "b": 2
}
// {a:1, b:2}

Inside the context, the previous entries can be accessed.

{
  a: 2,
  b: a * 2
}
// {a:2, b:4}

A context value can embed other context values.

{
  a: 1,
  b: {
    c: 2
  }
}
// {a:1, b:{c:2}}

Get entry/path

a.b

Accesses the entry with the key b of the context a. The path is separated by a dot ..

If the value of the entry b is also a context, the path can be chained (i.e. a.b.c).

{a: 2}.a
// 2

{a: {b: 3}}.a
// {b: 3}

{a: {b: 3}}.a.b
// 3

If the context a doesn't contain an entry with the key b, the expression returns null.

{a: 1}.b
// null

{a: 1}.b.c
// null

Filter

a[c]

Filters the list of context elements a by the condition c. The result of the expression is a list that contains all elements where the condition c evaluates to true. The other elements are excluded.

While filtering, the current element is assigned to the variable item and its entries can be accessed by their key.

[
  {
    a: "p1",
    b: 5
  },
  {
    a: "p2",
    b: 10
  }
][b > 7]
// [{a: "p2", b: 10}]

Projection

a.b

Extracts the entries with the key b of the list of context elements a (i.e. a projection). It returns a list containing the values of the context elements with the key b.

[
  {
    a: "p1",
    b: 5
  },
  {
    a: "p2",
    b: 10
  }
].a
// ["p1", "p2"]

If an element of the list a doesn't contain an entry with the key b, the result contains null of this element.

[
  {
    a: "p1",
    b: 5
  },
  {
    a: "p2",
    c: 20
  }
].b
// [5, null]