json-filter

Match an object against a filter

JSON Filter

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

$ npm install json-filter

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:

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

{
  name: {$present: true}
}

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

{
  description: {$any: true}
}

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

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

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

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

The value can only be one of the ones specified.

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

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

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

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']}
    }
  ]
}

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

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

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}
}
var checkFilter = require('json-filter')
  • 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