json-filter

Match an object against a filter

npm install json-filter
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JSON Filter

Match JSON objects against filters - used internally by JSON Context, Realtime Templates and ContextDB.

Installation

$ npm install json-filter

Filters

Filters are just object that have the keys and values you want your final object to have. e.g. if you wanted to require that the field type was always person your filter would be {type: 'person'}.

If things aren't so black and white, the following conditionals are available:

$present

Specify that the value must not be null or false (i.e. 'truthy').

{
  name: {$present: true}
}

$any

Specify that the value can be anything. Useful when matching all keys.

{
  description: {$any: true}
}

$contains

For matching against an array. The array must contain all of the values specified.

{
  tags: {$contains: ['cat', 'animal']}
}

$excludes

For matching against an array. The array cannot contain any of the values specified.

{
  permissions: {$excludes: ['admin', 'mod']}
}

$only

The value can only be one of the ones specified.

{
  gender: {$only: ['male', 'female', 'unknown']}
}

$not

The value can be anything except one of the ones specified.

{
  browser: {$not: ['IE', 'Fifefox']}
}

$matchAny

Allows a filter to branch into multiple filters when at least one must match.

{
  $matchAny: [
    { type: "Post"
      state: {$only: ['draft', 'published']}
    },
    { type: "Comment"
      state: {$only: ['pending', 'approved', 'spam']}
    }
  ]
}

$query

Specify a query to get the value to match. Uses options.queryHandler.

{
  type: 'item',
  user_id: {$query: 'user.id'}
}

$optional

A shortcut for specifying a lot of $any filters at the same time.

{
  $optional: ['description', 'color', 'age']
}

Is equivelent to:

{
  description: {$any: true},
  color: {$any: true},
  age: {$any: true}
}

API

var checkFilter = require('json-filter')

checkFilter(source, filter, options)

options:

  • match: specify: 'filter', 'source', 'any', 'all'
    • filter: every filter permission must be satisfied (i.e. required fields)
    • source: every source key must be specified in filter
    • any: the keys don't matter, but if there is a match, they must pass
    • all: all keys must be exactly the same, otherwise fails - for finding changed items - no $conditionals work in this mode
  • queryHandler: Accepts a function(query, localContext) that returns resulting value
  • context: Object to pass to the query handler
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