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json.set() Function

Introduced in version 1.3b49
Sets the value in at the specified index in a JSON Array or for the specified key in a JSON Object. You can use an empty string ("") to represent a new JSON Array or JSON Object.


newarr=json.set(jarr, [])
newarr=json.set(jarr, index, value)
newarr=json.set(jarr, index, value, ..., ...)
newobj=json.set(jobj, key, value)
newobj=json.set(jobj, key, value, ..., ...)


  • jarr - The JSON Array that has an index's value set.
  • index - The numeric index which has its value set.
  • jobj - The JSON Object that has a key's value set.
  • key - The named key which has its value set.
  • value - The content that is set to the index or key.

Note: The index and value parameters or key and value parameters can be repeated in pairs.

Note: newarr or newobj can be equal to jarr or jobj. In this case, the object/array will simply be updated.

Note: The word "class" is a reserved word in JavaScript; it is therefore not possible to create a JSON object containing a key named "Class," "class," or any mix of upper- and lower-case. MapTool will ignore any instructions to set a JSON object key with that name.


  [json.set("{}", "a", 5)]
  [json.set("", "a", 5, "b", 8)]
  [json.set(json.fromList("1,3"), 0, 8)]


 {"a":5, "b":8}
 [8, 3]

To save the new value in the JSON Array or JSON Object so that you can reference it later in a macro, you must set the array equal to the result of json.set().

   [myArray = json.append("", 1, 2, 3)]
   [myArray = json.set(myArray, 0, 5)]



See Also