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$jsonArrayUnshift

$jsonArrayUnshift adds a value to the front of a JSON array. All existing elements shift up by one position.

Syntax

$jsonArrayUnshift[Key;...;Value]

• Key: one or more keys forming the path to the array.
• Value: the value to add at the front.

What happens

1. $jsonParse loads the JSON object.
2. $jsonArrayUnshift inserts the value at index 0 of the array at the given key path.
3. All existing elements move up by one index.
4. Nothing is returned. Use $jsonJoinArray or $json to see the result.

Example 1: Add to the front of an array

$nomention
$jsonParse[{"music":["Ping! 2","Tokyo"\]}]
$jsonArrayUnshift[music;Paranoid]
$jsonJoinArray[music;, ]

What happens:

1. $jsonParse loads the object.
2. $jsonArrayUnshift[music;Paranoid] inserts Paranoid at the front.
3. $jsonJoinArray shows the result.

Output:

Paranoid, Ping! 2, Tokyo

Example 2: Prepend multiple values

$nomention
$jsonParse[{"queue":["third"\]}]
$jsonArrayUnshift[queue;second]
$jsonArrayUnshift[queue;first]
$jsonJoinArray[queue;, ]

What happens:

1. $jsonParse loads the object with a single-item array.
2. $jsonArrayUnshift[queue;second] inserts second at position 0.
3. $jsonArrayUnshift[queue;first] inserts first at position 0.
4. $jsonJoinArray shows the result.

Output:

first, second, third

Common uses

• Priority queues: insert high-priority items at the front
• Reverse chronological logs: add new entries to the top of a list
• Prepending values: add something before all existing elements

See also

• $jsonArrayAppend: to add to the end instead
• $jsonArrayShift: to remove from the front
• $jsonJoinArray: to display the array as a string