parse_json() function

Learn how to use the parse_json() function to return an object of type dynamic.

Interprets a string as a JSON value and returns the value as dynamic. If possible, the value is converted into relevant data types. For strict parsing with no data type conversion, use extract() or extract_json() functions.

It’s better to use the parse_json() function over the extract_json() function when you need to extract more than one element of a JSON compound object. Use dynamic() when possible.

Syntax

parse_json(json)

Parameters

NameTypeRequiredDescription
jsonstring✔️The string in the form of a JSON-formatted value or a dynamic property bag to parse as JSON.

Returns

An object of type dynamic that is determined by the value of json:

  • If json is of type dynamic, its value is used as-is.
  • If json is of type string, and is a properly formatted JSON string, then the string is parsed, and the value produced is returned.
  • If json is of type string, but it isn’t a properly formatted JSON string, then the returned value is an object of type dynamic that holds the original string value.

Example

In the following example, when context_custom_metrics is a string that looks like this:

{"duration":{"value":118.0,"count":5.0,"min":100.0,"max":150.0,"stdDev":0.0,"sampledValue":118.0,"sum":118.0}}

then the following query retrieves the value of the duration slot in the object, and from that it retrieves two slots, duration.value and duration.min (118.0 and 110.0, respectively).

datatable(context_custom_metrics:string)
[
    '{"duration":{"value":118.0,"count":5.0,"min":100.0,"max":150.0,"stdDev":0.0,"sampledValue":118.0,"sum":118.0}}'
]
| extend d = parse_json(context_custom_metrics)
| extend duration_value = d.duration.value, duration_min = d.duration.min

Notes

It’s common to have a JSON string describing a property bag in which one of the “slots” is another JSON string.

For example:

let d='{"a":123, "b":"{\\"c\\":456}"}';
print d

In such cases, it isn’t only necessary to invoke parse_json twice, but also to make sure that in the second call, tostring is used. Otherwise, the second call to parse_json will just pass on the input to the output as-is, because its declared type is dynamic.

let d='{"a":123, "b":"{\\"c\\":456}"}';
print d_b_c=parse_json(tostring(parse_json(d).b)).c

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