Jsonata

Predicates

You can select an object using a predicate expression (some expression that evaluates to true or false using [] square brackets.

You can match an object in an array by adding [] square brackets and using an = equals sign with the field you want to select.

// Data 01
{
  "Organisation": "Thunkcorp",
  "Users": [
    {
      "name": "John",
      "age": 20,
      "height": 185
    },
    {
      "name": "Mark",
      "age": 10
    }
  ]
}

Query for the example data Data 01…

Users[age='10'] =>
{
  "name": "Mark",
  "age": 10
}

You can select a sub property on a matched object using the standard . dot syntax.

// Query on Data 01
Users[age='10'].name =>
"Mark"

You can select a property based on whether it exists for data with irregular formatting by using placing the name of a property in the [] predicate.

// Query on Data 01
Users[height] =>
{
  "name": "John",
  "age": 20,
  "height": 185
},

You can select a higher level on a nested match by nesting [] square brackets containing predicates.

// Data 02
{
  "Users": [
    {
      "name": "John",
      "age": 20,
      "Addresses": [
        {
		  "Number": 20
        },
        {
          "Number": 25
        }
      ]
    },
    {
      "name": "Mark",
      "age": 10,
      "Addresses": [
        {
		  "Number": 40
        }
      ]
    }
  ]
}

Nested query for the example data Data 02. Notice that query returns the entirety of the user object even though the match is made on a lower level property.

// Query on Data 02
Users[Addresses[Number=20]] =>
{
  "name": "John",
  "age": 20
  "Addresses": [
    {
     "Number": 20
    }
  ]
}

You can execute functions within predicate expressions to filter objects based on conditions. In the example below the $count function is used to get the length of the array and then the conditional >1 is used on the result. This is then evaluated in the [] brackets and applied as a predicate to select.

// Query on Data 02
Users[$count(Addresses)>1] =>
{
  "name": "John",
  "age": 20
  "Addresses": [
    {
     "Number": 20
    },
    {
      "Number": 25
    }
  ]
}

You can filter an array based on its contents by using the in in-fix function within a predicate.

// Data 03
[
  {
    "data": [1, 2, 3]
  },
  {
    "data": [4, 5, 6]
  }
]

Query for example Data 03 selects only the object which has a 4 occurring in its data property.

*[4 in data] =>
{
  "data": [4, 5, 6]
}

Functions

You can execute simple functions on object properties such us combination by using () brackets with operators after the property you are selecting with . dot syntax. The & syntax below is used for concatenating strings, but you can use standard numeric operators for purely numeric data.

// Query on Data 02
Users.(name & " " & age) =>
[
  "John, 20",
  "Mark, 10"
]

You can concatenate the results of two arrays using the $append function. This is useful for combining the results of two queries on a data set.