在源代码中使用 `index.d.ts` 声明文件

Question

我想index.d.ts在将纯.js文件移植到.ts我的项目中时重用其中的类型定义。但是我得到Cannot find name 'Type'.

我觉得这是我遇到的一些配置问题。任何帮助，非常感谢 - 谢谢。

文件夹结构如下

<root>
  - /javascript (all js files)
  index.d.ts    (declarations)

这是我当前的 tsconfig.json

{
  "compilerOptions": {
    /* Basic Options */
    "target": "es2017",                       /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
    "lib": [ "es2017" ],                      /* Specify library files to be included in the compilation. */
    "allowJs": true,                          /* Allow javascript files to be compiled. */
    // "checkJs": true,                       /* Report errors in .js files. */
    "jsx": "react-native",                    /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
    // "declaration": true,                   /* Generates corresponding '.d.ts' file. */
    // "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. */
    // "sourceMap": true,                     /* Generates corresponding '.map' file. */
    // "outFile": "./",                       /* Concatenate and emit output to single file. */
    // "outDir": "./",                        /* Redirect output structure to the directory. */
    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    // "composite": true,                     /* Enable project compilation */
    // "removeComments": true,                /* Do not emit comments to output. */
    "noEmit": true,                           /* Do not emit outputs. */
    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */

    /* Strict Type-Checking Options */
    "strict": true,                           /* Enable all strict type-checking options. */
    // "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. */
    // "strictNullChecks": true,              /* Enable strict null checks. */
    // "strictFunctionTypes": true,           /* Enable strict checking of function types. */
    // "strictBindCallApply": true,           /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
    // "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. */
    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */
    "skipLibCheck": true,                     /* Skip type checking of all declaration files (*.d.ts). */

    /* Additional Checks */
    "forceConsistentCasingInFileNames": true,
    // "noUnusedLocals": true,                /* Report errors on unused locals. */
    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */

    /* Module Resolution Options */
    "moduleResolution": "node",               /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
    "baseUrl": "./javascript",                /* Base directory to resolve non-absolute module names. */
    // "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
    // "typeRoots": [],                       /* List of folders to include type definitions from. */
    // "types": [],                           /* Type declaration files to be included in compilation. */
    "allowSyntheticDefaultImports": true,     /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
    "esModuleInterop": true,                  /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
    "resolveJsonModule": true,
    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */

    /* Source Map Options */
    // "sourceRoot": "",                      /* Specify the location where debugger should locate TypeScript files instead of source locations. */
    // "mapRoot": "",                         /* Specify the location where debugger should locate map files instead of generated locations. */
    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */

    /* Experimental Options */
    // "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
    // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
  }
}

Answer 1

在 JavaScript 项目中，您必须index.d.ts自己维护，但是一旦项目转换为 TypeScript（并且declaration选项在 tsconfig.json 中取消注释）index.d.ts，则由 tsc 生成。拥有一个带有自我维护的 TypeScript 项目听起来并不是一个好主意index.d.ts。

也许您只需要转换您的项目并维护相同的导出接口。

要实现这一点，您只需要在index.d.ts转换后的 TypeScript 文件中使用相同的声明（剪切和粘贴声明并使用定义丰富它们）。

让我们来测试一个简单的 JavaScript 包：

function charcatersCount(str) {
  return str.length;
}

module.exports = { charactersCount };

手工维护的index.d.ts文件将如下所示：

export declare function charactersCount(str: string): number;

我的建议是打开一个新创建的index.ts文件，剪切并粘贴声明并将它们从声明更改为定义

export function charactersCount(str: string): number {}

最后用实际的定义丰富它们：

export function charactersCount(str: string): number {
  return str.length;
}

对每个导出的函数/类/常量/变量重复此操作。

现在tsc使用declaration选项运行（--declaration从命令行或"declaration": true,在tsconfig.json文件中）将生成一个index.js文件（编译版本）和一个index.d.ts与源文件或多或少相同的文件（声明文件）。

从现在开始，您将不再需要index.d.ts手动维护您的文件：每次您更改包时tsc都会产生它。

关于具体错误Cannot find name 'Type'，我需要查看生成它的代码。

希望这可以帮助。