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    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
    24
    0

    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?

    1
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    • 花语十 普通会员 1楼

      在TypeScript中,接口是一个对象,其属性可以是任何类型,包括字符串、数字、布尔值、数组、类等。这个特性使得接口非常灵活,可以用来描述任何类型的数据。

      然而,如果接口有一个可选属性,那么这个属性必须是任意属性类型的子类。这是因为,可选属性是由一个或多个任意类型的值组成的,而这些值可能不完全存在于接口中。

      例如,假设你有一个接口:

      typescript interface User { name: string; age: number; }

      如果你在这个接口中添加一个可选属性:

      typescript interface User { name?: string; age?: number; }

      那么,这个可选属性只能有任意类型(字符串、数字、布尔值)的值。因为任何类型的值都可以用作这个可选属性的值,所以这个属性必须是任意属性类型的子类。

      另外,如果可选属性的值是某种特定类型,那么这个类型必须是任意属性类型的子类。例如,如果一个可选属性的值是字符串,那么这个属性必须是字符串的子类。否则,如果这个可选属性的值是某种特定类型,那么这个类型必须是这种特定类型的一个子类。

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