continue to deal the result as a array after filter

[NingGelin]

Motivation

I have a json like this:

{
 "contactMedium": [
 {
 "@type": "EmailContactMedium",
 "preferred": true,
 "contactType": "other",
 "validFor": {
 "startDateTime": "2018-10-22T08:31:52.028Z"
 },
 "emailAddress": "tom@email.com"
 },
 {
 "@type": "GeographicAddressContactMedium",
 "preferred": true,
 "contactType": "other",
 "validFor": {
 "startDateTime": "2018-10-22T08:31:52.028Z"
 },
 }
 ]
}

I want to get the number of item with preferred==true
const result = JSONPath({ path: '$.contactMedium[?(@.preferred==true)].length', json: data })

Current behavior

got []

Desired behavior

got 2

Alternatives considered

currently, i can got the result expected by this way.
const result = JSONPath({ path: '$.contactMedium[?(@.preferred==true)]', json: data })
console.log(result)

const result2 = JSONPath({ path: '$.length', json: result })
console.log(result2)

[gerad]

+1 to this issue. I think I can get my company to sponsor the fix (depending on the cost).

[80avin]

@NingGelin I am not able to understand the use-case.

Why can't we use something like

const data = {
 "contactMedium": [
 {
 "@type": "EmailContactMedium",
 "preferred": true,
 "contactType": "other",
 "validFor": {
 "startDateTime": "2018-10-22T08:31:52.028Z"
 },
 "emailAddress": "tom@email.com"
 },
 {
 "@type": "GeographicAddressContactMedium",
 "preferred": true,
 "contactType": "other",
 "validFor": {
 "startDateTime": "2018-10-22T08:31:52.028Z"
 },
 }
 ]
}
const result = JSONPath({ path: '$.contactMedium[?(@.preferred==true)]', json: data }).length

[brettz9]

I think the use case would be for applications which exposed JSONPath expressions to users, and to allow the users to make a query which performed a count.

We should probably not be making custom additions to the JSONPath standard now though, so I would discuss any new proposals (e.g., for a count function) with the standards-making body if there is not already one in effect.

[captn3m0]

Explicit use-case: https://img.shields.io/badges/dynamic-json-badge supports jsonpath-plus

I'd like to count the number of dependencies. I can generate a badge using $.dependencies.*~:

But adding .length fails:

URL: https://img.shields.io/badge/dynamic/json?url=https%3A%2F%2Fgithub.com%2Fbadges%2Fshields%2Fraw%2Fmaster%2Fpackage.json&query=%24.dependencies.*~

[80avin]

Interesting!
To decide whether JSONPath should support such functions or not, I went on to understand XPath and looks like XPath supports count() function.

I think this is a strong enough argument for JSONPath to support such functions, though it may take time.
Moreover, considering attempts to standardize the JSONPath schema, we need to work on designing a schema also.