70 lines
2.7 KiB
Plaintext
70 lines
2.7 KiB
Plaintext
title: JSON in TiddlyWiki
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tags: Features
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type: text/vnd.tiddlywiki
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created: 20220427174702859
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modified: 20220611104737314
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!! Introduction
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JSON (~JavaScript Object Notation) is a standardised text representation for data structures that is widely used for the storage and transfer of data.
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JSON is used in several different contexts in TiddlyWiki. For example:
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* Tiddlers are represented as JSON data within TiddlyWiki HTML files
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* Groups of tiddlers can be [[exported|How to export tiddlers]] and [[imported|Importing Tiddlers]] as JSON files
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* Plugin tiddlers store their constituent shadow tiddlers as JSON data
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* The client-server configuration uses [[JSON messages|TiddlyWeb JSON tiddler format]] to communicate between the client and the server
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* Arbitrary JSON data within DataTiddlers can be processed and manipulated using a set of filter operators and action widgets
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!! About JSON
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The technical description of JSON at the official website https://json.org/ is terse. Here we summarise the main features.
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JSON supports two basic data structures:
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''Arrays'' are lists of items. The items are identified by their numeric index (starting at zero)
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An example of an array is:
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```json
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["one","two","three\"four"]
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```
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Note the following features of arrays:
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* The array is signified by square brackets surrounding the list of items
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* Each item is a string in double quotes. Double quotes can be included within the strings by preceding them with a backslash (`\`)
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* The items are separated by commas
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''Objects'' are collections of name/value pairs. Each item is a value that is identified by a unique name
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An example of an object is:
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```json
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{
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"first": "This is the first value",
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"second": "This is the second value",
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"third": "This is the third value"
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}
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```
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Note the following features of objects:
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* The object is signified by curly braces surrounding the list of name/value pairs
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* Each name/value pair consists of the name in double quotes, a colon, and then the value
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* The name/value pairs are separated by commas
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The examples above all show string values. JSON actually supports several different types of value. Any of these types can be used as a value:
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* String values, as shown above
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* Numeric values, represented as signed decimals such as `1`, `3.14`. Exponential notation can also be used e.g. `-1E10`
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* Boolean values, represented by the keywords `true` and `false`
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* The special value `null`, which is often used to represent data that is missing or incomplete
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* Objects and arrays are also values, allowing complex nested structures to be represented
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!! Working with Data Tiddlers
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* [[Reading data from JSON tiddlers]]
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* [[Constructing JSON tiddlers]]
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* [[Modifying JSON tiddlers]]
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