Json Schema, take into account unspecified properties - json

Question

Is there is any ways to get heads ups about properties which are not described by schema into the standard. For example this schema:
{
"description": "foo and bar",
"type": "object",
"properties": {
"foo": {
"type": "number"
},
"bar": {
"type": "string",
"enum": [
"a",
"b",
"c"
]
}
}
}
Will pass this JSON:
{
"foo": 12345,
"bar": "a",
"baz": 12312
}
Although it has baz property which is not the part of schema.
UPD: As of now I'm using tv4 library.

Answer 1

Option 1: additionalProperties in the schema
If you want to explicitly constrained to the properties listed in a particular properties definition, then you can use additionalProperties: false. This will restrict data to only using properties defined in the nearby properties entry - in this case, "foo" and "bar".
However, use of additionalProperties impacts schema extension. If you (or someone else) extends this schema later (using allOf/$ref), then the data will still be subject to this schema - so will only be allowed to use "foo" and "bar", regardless of definitions elsewhere.
Option 2: banUnknownProperties flag in tv4
If the kind of complete lock-down is not desired, then you can use the banUnknownProperties flag in tv4 (docs). Basically, after validation, any properties that were not accounted-for by any schemas are raised as errors.
It was designed for cases when extra properties (including future variations/extensions) are theoretically allowed in the data format, but you want (for testing/warning purposes) to be alerted when extra properties show up where you're not expecting them.