自动生成typescript类型声明工具实现详解

npm install -g my-json-to-ts

my-json-to-ts input.json output.ts

--name 类型名称    # 指定转换后的类型名称，默认为 JsonType
--namespace 命名空间 # 指定转换后的命名空间，默认为无
--no-file          # 不将转换后的 TypeScript 类型定义保存为文件

{
  "name": "John",
  "age": 30,
  "address": {
    "city": "New York",
    "state": "NY"
  },
  "hobbies": [
    "reading",
    "traveling"
  ]
}

interface JsonType {
  name: string;
  age: number;
  address: {
    city: string;
    state: string;
  };
  hobbies: string[];
}

{
  "name": "John",
  "age": 30,
  "address": {
    "city": "New York",
    "state": "NY",
    "postalCode": 10001
  },
  "friends": [
    {
      "name": "Jane",
      "age": 28,
      "address": {
        "city": "Los Angeles",
        "state": "CA"
      }
    },
    {
      "name": "Bob",
      "age": 35,
      "address": {
        "city": "ChicaGo",
        "state": "IL"
      }
    }
  ],
  "hobbies": [
    "reading",
    "traveling",
    {
      "name": "swimming",
      "location": "pool"
    }
  ]
}

interface JsonType {
  name: string;
  age: number;
  address: {
    city: string;
    state: string;
    postalCode: number;
  };
  friends: {
    name: string;
    age: number;
    address: {
      city: string;
      state: string;
    };
  }[];
  hobbies: (string | {
    name: string;
    location: string;
  })[];
}

  const fs = require('fs-extra');
  const commander = require('commander');
  
  function jsonToTs(object, name = 'JsonType', namespace) {
      const getType = value => {
          let typeRes = ``;
          if (Array.isArray(value)) {
              value.forEach(item => {
                  let subType = getType(item);
                  if (typeRes.split('|').indexOf(subType) < 0) {
                      typeRes += subType
                      typeRes += "|"
                  }
              })
              typeRes = typeRes.substring(0, typeRes.length - 1)
               if (typeRes.split('|').length > 1) {
                  return `(${typeRes})[]`;
                } else {
                  return `${typeRes}[]`;
                }
          }
          if (typeof value === 'object' && value !== null) {
              const props = Object.entries(value)
                  .map(([key, val]) => `${key}: ${getType(val)}`)
                  .join('; ');
              return `{ ${props} }`;
          }
          return typeof value;
      };
      const type = getType(object);
      const declaration = `interface ${name} ${type}`;
      return namespace ? `namespace ${namespace} { \r\n ${declaration} \r\n}` : declaration;
  }
  
  async function readJson(path) {
      const content = await fs.readFile(path, 'utf8');
      return JSON.parse(content);
  }
  
  async function writeTs(content, path) {
      await fs.writeFile(path, content, 'utf8');
  }
  
  async function jsonToTsFile(inputPath, outputPath, options) {
      const { name, namespace, noFile } = options
      try {
          const object = await readJson(inputPath);
          const type = jsonToTs(object, name, namespace);
          if (noFile) {
              console.log(type);
          } else {
              await writeTs(type, outputPath);
              console.log(`Type definition saved to ${outputPath}`);
          }
      } catch (err) {
          console.error(err.message);
      }
  }
  const program = new commander.Command();
  program
      .arguments('<input> <output>')
      .option('--no-file', 'do not save to file')
      .option('-s, --namespace <namespace>', 'type namespace')
      .option('-n, --name <name>', 'type name', 'JsonType')
      .action(jsonToTsFile);
  program.parse(process.argv);