JSON schema v4 hack for 'contains'.js

var tv4 = require('tv4');

var schema = {
  "type": "object",
  "$schema": "http://json-schema.org/draft-04/schema",
  "id": "#",
  "required": ["events"],
  "properties": {
    "events": {
      "type": "array",
      "minItems": 1,
      "not": {
        "items": {
          "type": "object",
          "required": ["event_name"],
          "properties": {
            "event_name": {
              "type": "string",
              "not": {
                "enum": ["inventory sent"]
              }
            }
          }
        }
      }
    }
  }
};

var data = {
  "events":[
    { "event_name": "foo" },
    { "event_name": "inventory sent" },
    { "event_name": "foo" }
  ]
};

console.log(tv4.validateMultiple(data, schema));

This validates the "events" object, and requires that at least one item in that array has a the property "event_name" with the value "inventory sent".

JSON schema v4 does not have a native validation keyword for this so a double negative has to be used:

• array must not not have an event of type "inventory sent"

...which can be simplified to...

• array must not not have an event of type "inventory sent"

v5 has a proposed "contains" that does exactly what we want but it is not released yet...

I've been looking for a good example on this. Thanks!