关于typescript接口的确定属性和可选属性的类型必须是任意属性类型的子类的疑惑

第一种情况:

interface Woman {
  name: number;
  [properName: number]: string;
}

let woman: Woman = {
  name: 1,
  1: "Hannah"
};

第二种情况:

interface Woman {
  name: string;
  [properName: number]: number;
}

let woman: Woman = {
  name: "Hannah",
  1: 1
};

按照规则:

typescript接口的确定属性和可选属性的类型必须是任意属性类型的子类

无论上述哪种情况编译的时候应该都报错吧?因为number不是string类型的子类,反过来string也不是number类型的子类啊?
可是实际情况是,两种情况多没报错。
这个是tsconfig.json的配置:

{
  "compilerOptions": {
    /* Basic Options */
    // "incremental": true,                   /* Enable incremental compilation */
    "target": "es5" /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019' or 'ESNEXT'. */,
    "module": "commonjs" /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */,
    // "lib": [],                             /* 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": "preserve",                     /* 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": "./dist/" /* Redirect output structure to the directory. */,
    "rootDir": "./src/" /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */,
    // "composite": true,                     /* Enable project compilation */
    // "tsBuildInfoFile": "./",               /* Specify file to store incremental compilation information */
    // "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. */

    /* Additional Checks */
    // "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": "./",                       /* 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'. */,
    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */
    // "allowUmdGlobalAccess": true,          /* Allow accessing UMD globals from modules. */

    /* 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. */

    /* Advanced Options */
    "forceConsistentCasingInFileNames": true /* Disallow inconsistently-cased references to the same file. */
  }
}

难道和配置有关?

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2 个回答

你有疑问的是文档里的这句话吧

TypeScript支持两种索引签名:字符串和数字。 可以同时使用两种类型的索引,但是数字索引的返回值必须是字符串索引返回值类型的子类型。 这是因为当使用 number来索引时,JavaScript会将它转换成string然后再去索引对象。 也就是说用 100(一个number)去索引等同于使用"100"(一个string)去索引,因此两者需要保持一致。

这个意思你可能没理解对,上述描述的不一致情况是下面这样子的定义:

interface Woman {
  name: number; // 报错了
  [properName: string]: string;
}

interface Man {
  1: string; // 报错了
  [properName: number]: number;
}
新手上路,请多包涵

我也是看楼主看的ts教程感到疑惑就过来的, 翻阅官方文档可以看到:While string index signatures are a powerful way to describe the “dictionary” pattern, they also enforce that all properties match their return type. This is because a string index declares thatobj.propertyis also available asobj["property"].
官方文档中好像没有任意属性这个说法,你说的任意属性应该就是索引类型为string的索引属性,这类属性要满足你说的规则,但是索引类型为number的索引属性是不需要满足这个规则的.
文档链接

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