Convert TypeScript interfaces and types to JSON Schema definitions with property type mapping.
TypeScript interfaces and type aliases become JSON Schema documents here: each property is mapped to its schema type, arrays get an items keyword, unions of literals become an enum, and the required array is rebuilt from your ? optional markers. Two things usually surprise people. First, TypeScript has no required keyword - a converter's only signal for what belongs in required is the question mark, so a property written without one is assumed required even when real data often lacks it. Second, this tool converts any and unknown to an empty schema {} that accepts anything, and Date conventionally maps to a string with a date-time format. The conversion runs entirely in the browser; nothing you paste is uploaded.
A concrete input and expected output from the current implementation.
Input
type User = {
id: number;
name?: string;
tags: string[];
role: 'admin' | 'member';
}; Expected output
{
"type": "object",
"properties": {
"id": { "type": "number" },
"name": { "type": "string" },
"tags": { "type": "array", "items": { "type": "string" } },
"role": { "enum": ["admin", "member"] }
},
"required": ["id", "tags", "role"]
} name carries the ? marker, so it appears in properties but not in the required array, while the other three properties are listed there. tags becomes an array with an items schema, and the two-element string literal union collapses into an enum listing exactly 'admin' and 'member'.
The tool parses the TypeScript source you paste, picks out the interfaces, type aliases, and inline object literals it finds, then walks each declared shape. Scalar types map one-to-one - string becomes type: string, number becomes type: number, boolean becomes type: boolean - arrays gain an items keyword, nested object types become nested properties blocks, and the optional marker ? decides which properties are listed in the required array.
Nullable unions such as string | null typically become a type array listing both, ['string', 'null']; a union of string literals becomes an enum; and Date follows the widespread convention of a string carrying format date-time. This tool maps types that JSON Schema cannot express - functions, promises, class instances, generic instantiations - to an empty schema {} that accepts any value, so a suspiciously permissive property usually points at an unmappable type rather than a deliberate choice.
The question mark. Converters derive required membership solely from the ? marker, so name: string is required and name?: string is not. If a field is genuinely optional in the runtime data, mark it optional in the type. If it is always present but sometimes null, model it as string | null and validate the null case instead.
Only if the output sets additionalProperties: false. TypeScript never forbids extra keys at runtime - its excess-property checks happen at compile time - and JSON Schema permits unknown keys unless the schema explicitly forbids them. Check what the tool emitted for additionalProperties, and add the keyword yourself if strictness matters.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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