66 lines
2.0 KiB
Plaintext
66 lines
2.0 KiB
Plaintext
created: 20220611104737314
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modified: 20220611104737314
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tags: [[Filter Operators]] [[JSON Operators]]
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title: jsonindexes Operator
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caption: jsonindexes
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op-purpose: retrieve the value of a property from JSON strings
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op-input: a selection of JSON strings
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op-parameter: one or more indexes of the property to retrieve
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op-output: the values of each of the retrieved properties
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<<.from-version "5.2.4">> See [[JSON in TiddlyWiki]] for background.
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The <<.op jsonindexes>> operator is used to retrieve the property names of JSON objects or the index names of JSON arrays. See also the following related operators:
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* <<.olink jsonget>> to retrieve the values of a property in JSON data
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* <<.olink jsontype>> to retrieve the type of a JSON value
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* <<.olink jsonextract>> to retrieve a JSON value as a string of JSON
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Properties within a JSON object are identified by a sequence of indexes. In the following example, the value at `[a]` is `one`, and the value at `[d][f][0]` is `five`.
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```
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{
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"a": "one",
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"b": "",
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"c": "three",
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"d": {
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"e": "four",
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"f": [
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"five",
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"six",
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true,
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false,
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null
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],
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"g": {
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"x": "max",
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"y": "may",
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"z": "maize"
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}
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}
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}
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```
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The following examples assume that this JSON data is contained in a variable called `jsondata`.
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The <<.op jsonindexes>> operator uses multiple parameters to specify the indexes of the property to retrieve:
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```
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[<jsondata>jsonindexes[d],[f]] --> "0", "1", "2", "3", "4"
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[<jsondata>jsonindexes[d],[g]] --> "x", "y", "z"
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```
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Indexes can be dynamically composed from variables and transclusions:
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```
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[<jsondata>jsonindexes<variable>,{!!field}]
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```
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Retrieving the indexes of JSON properties that are not objects or arrays will return nothing.
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A subtlety is that the special case of a single blank parameter is used to identify the root object. Thus:
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```
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[<jsondata>jsonindexes[]] --> "a", "b", "c", "d"
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```
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