inferSchema

Infer a SchemaNode tree from any JSON value.

Signature

typescript

function inferSchema(value: unknown, options?: InferOptions): SchemaNode;

Options

Option	Type	Default	Description
`mode`	`"sampled" \| "exhaustive"`	`"sampled"`	`sampled` picks 3 elements (first, middle, last). `exhaustive` infers every element.
`maxDepth`	`number`	`10`	Maximum recursion depth. Objects/arrays beyond this depth become opaque `{}` or count-only.

Try it: Primitives

The four primitive types: string (with character length), number, boolean, null.

Input

{
  "name": "Alice",
  "age": 30,
  "active": true,
  "deleted": null
}

Output

Try it: Array of Objects

All elements have the same keys — no optional marking needed.

Input

[
  { "id": 1, "name": "Alice" },
  { "id": 2, "name": "Bob" }
]

Output

Try it: Optional Keys

Some elements have email, others don't — the schema marks it optional: true. The label key only appears on one element but is still discovered.

Input

[
  { "id": 1, "name": "Alice", "email": "alice@test.com" },
  { "id": 2, "name": "Bob" },
  { "id": 3, "name": "Charlie", "email": "charlie@test.com", "label": "VIP" }
]

Output

Try it: Varying Array Sizes

Nested arrays with different lengths across elements get varyingSizes: true instead of a misleading count.

Input

[
  { "id": 1, "tags": ["admin", "user", "beta"] },
  { "id": 2, "tags": ["user"] },
  { "id": 3, "tags": ["user", "beta"] }
]

Output

Try it: Mixed Types (Union)

When array elements have different types, the schema produces a union. Switch between sampled and exhaustive to see how sampling can miss elements.

Input

[
  { "id": 1 },
  { "id": 2 },
  { "id": 3 },
  "oops",
  [99]
]

Output

Try it: Union Deduplication

Multiple objects merge into one variant with a variantCount. Here 3 objects become one variant with variantCount: 3.

Input

[
  { "id": 1 },
  { "id": 2 },
  { "id": 3 },
  "stray",
  [99]
]

Output

Try it: Mixed Value Types per Key

When the same key has different types across objects (e.g. value_code is sometimes a string, sometimes a number), the schema produces a union for that key.

Input

[
  { "code": "sim_count", "value_code": "dual_sim" },
  { "code": "ram_size", "value_code": 8 },
  { "code": "battery_size", "value_code": 3650 }
]

Output

Try it: Donor Elements (Sampled Mode)

With 7 elements, sampled picks indices [0, 3, 6]. The label key only exists on element 5 — not sampled. The donor mechanism discovers it by scanning all keys, then finding an element that has it to infer the type.

Input

[
  { "id": 1, "name": "Alice" },
  { "id": 2, "name": "Bob" },
  { "id": 3, "name": "Charlie" },
  { "id": 4, "name": "Diana" },
  { "id": 5, "name": "Eve" },
  { "id": 6, "name": "Frank", "label": "VIP" },
  { "id": 7, "name": "Grace" }
]

Output

Try it: Depth Control

Drag the maxDepth slider to see how depth limiting works. At depth 1, nested objects become opaque {}. At depth 2+, keys start appearing.

Input

{
  "product": {
    "details": {
      "specs": {
        "ram": "8GB",
        "storage": "128GB"
      }
    }
  }
}

Output

Try it: Deeply Nested (CMS-style)

Real-world CMS data with 7+ levels of nesting. At the default maxDepth: 10, banner objects are fully expanded.

Input

{
  "type": "static",
  "data": [
    {
      "modules": [
        {
          "type": "recentlySearched",
          "banners": [
            { "imageUrl": "abc", "title": "test" },
            { "imageUrl": "def", "title": "test2" }
          ]
        }
      ]
    }
  ]
}

Output

SchemaNode Structure

typescript

interface SchemaNode {
  type: "string" | "number" | "boolean" | "null" | "object" | "array" | "union";
  length?: number;         // string character count
  keys?: Record<string, SchemaNode>;  // object keys
  items?: SchemaNode;      // array item schema
  count?: number;          // array element count
  varyingSizes?: boolean;  // nested arrays with different lengths
  optional?: boolean;      // key only in some array elements
  variants?: SchemaNode[]; // union type variants
  variantCount?: number;   // elements matching this variant
}

inferSchema ​

Signature ​

Options ​

Try it: Primitives ​

Try it: Array of Objects ​

Try it: Optional Keys ​

Try it: Varying Array Sizes ​

Try it: Mixed Types (Union) ​

Try it: Union Deduplication ​

Try it: Mixed Value Types per Key ​

Try it: Donor Elements (Sampled Mode) ​

Try it: Depth Control ​

Try it: Deeply Nested (CMS-style) ​

SchemaNode Structure ​

inferSchema

Signature

Options

Try it: Primitives

Try it: Array of Objects

Try it: Optional Keys

Try it: Varying Array Sizes

Try it: Mixed Types (Union)

Try it: Union Deduplication

Try it: Mixed Value Types per Key

Try it: Donor Elements (Sampled Mode)

Try it: Depth Control

Try it: Deeply Nested (CMS-style)

SchemaNode Structure