JSON to TypeScript Types

---

• 🎯 Optional fields — auto-detects nullable fields and marks them as optional (?)
• 📝 .d.ts export — output ready-to-use declaration files
• 🏷️ Custom root name — control the top-level type name
• 🧹 No export mode — for inline type definitions
• ⚡ Zero config — works out of the box, no TypeScript project required

---

Global install (recommended)

npm install -g json-to-types

Or run via npx

npx json-to-types data.json

Or use as a dependency

npm install --save-dev json-to-types

---

# From a JSON file
json-to-types data.json

# From stdin with custom root type name
cat data.json | json-to-types --name ApiResponse

# Output to file
json-to-types data.json --output types.ts

# Generate .d.ts declaration file
json-to-types data.json --dts --output types.d.ts

# Disable optional field detection
json-to-types data.json --no-optional

# Omit export keyword
json-to-types data.json --no-export

# Custom indentation
json-to-types data.json --indent 4

---

|--------|-------|---------|-------------| | --name | -n | RootObject | Root type name | | --output | -o | stdout | Output file path | | --dts | -d | false | Output as .d.ts | | --no-optional | | true | Disable optional field detection | | --no-export | | true | Omit export keyword | | --indent | | 2 | Spaces per indent level |

---

import { convert, convertString } from 'json-to-types';

// From a parsed object const json = { name: 'John', age: 30, active: true }; const types = convert(json, { rootName: 'User' }); console.log(types);

// From a JSON string const types2 = convertString('{"id":1,"title":"Hello"}', { rootName: 'Post' });

---

```json
{ "name": "Alice", "age": 25, "active": true }

Output:

export interface RootObject {
name: string;
age: number;
active: boolean;
}

---

{
"user": {
"profile": {
"bio": "Developer",
"followers": 1200
}
}
}

Output:

export interface RootObjectSub1 {
bio: string;
followers: number;
}

export interface RootObjectSub2 {
profile: RootObjectSub1;
}

export interface RootObject {
user: RootObjectSub2;
}

---

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

Output:

export interface RootObjectSub1 {
id: number;
name: string;
}

export interface RootObject {
users: RootObjectSub1[];
}

---

{ "name": "Test", "description": null }

Output:

export interface RootObject {
name: string;
description?: null;
}

---

• Configuration files — generate types for JSON configs (.eslintrc, tsconfig, etc.)
• Mock data — turn mock JSON objects into proper TypeScript interfaces
• Legacy migration — quickly type existing JSON blobs in a TypeScript codebase
• Documentation — generate type stubs for API documentation

---

|---------|--------------|-------------| | Nested type names | ✅ Automatic | ❌ Often missing | | Array item dedup | ✅ Structural hash | ❌ Duplicate types | | Optional detection | ✅ Auto from null | ❌ Manual only | | .d.ts output | ✅ Built-in | ⚠️ Partial | | Zero dependencies | ✅ (only commander) | ❌ Heavy | | CLI + API | ✅ Both | ⚠️ Usually one |

---

• env-validator — Validate .env files against .env.example

---

• 🚀 Deploy your frontend on Vercel
• ⭐ Star this repo to help others discover it

---

---

🤝 赞助支持 (Sponsor)

如果这个项目对你有帮助，可以请我喝杯咖啡 ☕

• 💖 支付宝 (Alipay): 18559219554 | 邮箱联系: 530765059@qq.com
• ☁️ DigitalOcean 联盟链接: 免费 $200 额度
• ⭐ 在 GitHub 上点 Star 帮助更多人发现这个项目

📄 License