TypeScript Errors All In One

1. Property 'name' has no initializer and is not definitely assigned in the constructor.ts

属性"名称"没有初始化程序，并且在构造函数中未明确分配

Strict Class Initialization

--strictPropertyInitialization

https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-7.html#strict-class-initialization

class C {

  foo: number;

  bar = "hello";

  baz: boolean;

  // Property 'baz' has no initializer and is not definitely assigned in the constructor.ts(2564)

  constructor() {

    this.foo = 42;

  }

}

solutions

class CC {

  foo: number;

  bar = "hello";

  baz: boolean | undefined;

  constructor() {

    this.foo = 42;

  }

}

1. tsconfig.json 关闭 Strict Class Initialization

tsconfig.json

{

  "include": ["src/**/*"],

  "exclude": ["tests/**/*"],

  "compilerOptions": {

    "target": "es5",

    "module": "commonjs",

    "jsx": "preserve",

    "declaration": false,

    "declarationMap": false,

    "sourceMap": true,

    "outDir": "./build",

    "rootDir": "./",

    "removeComments": true,

    "downlevelIteration": true,

    "isolatedModules": false,

    "strict": true,

    "noImplicitAny": true,

    "strictNullChecks": true,

    "strictFunctionTypes": true,

    "strictPropertyInitialization": false,// 关闭

    "noImplicitThis": true,

    "alwaysStrict": true,

    "noUnusedLocals": true,

    "noUnusedParameters": true,

    "noImplicitReturns": true,

    "noFallthroughCasesInSwitch": true,

    "moduleResolution": "node",

    "esModuleInterop": true,

    "allowUmdGlobalAccess": true,

    "experimentalDecorators": true,

    "emitDecoratorMetadata": true,

    "skipLibCheck": true,

    "forceConsistentCasingInFileNames": true

  }

}

2. declaration for the 'Promise' constructor or include 'ES2015' in your --lib option

interface Promise Represents the completion of an asynchronous operation

An async function or method in ES5/ES3 requires the 'Promise' constructor.

Make sure you have a declaration for the 'Promise' constructor or include 'ES2015' in your --lib option.ts(2705)

const getRequestTo = async <R>(endpoint: string): Promise<ApiResponseInterface<R>> => {

  const request = await fetch(process.env.HOST + endpoint);

  const response = await request.json();

  return response;

};

const userResponse = getRequestTo('/user-data');

solution, How to fixed TypeScript Promise Error

just need to add a line of code"lib": ["es2015"], in your tsconfig.json

{

   // ...

  "compilerOptions": {

    "target": "es5",

    "module": "commonjs",

    "lib": ["es2015"],//

    // ...

  }

}

Cannot find name 'fetch'.ts(2304)

solution, How to fixed TypeScript fetch Error

just need to add a line of code"lib": ["DOM"], in your tsconfig.json

{

   // ...

  "compilerOptions": {

    "target": "es5",

    "module": "commonjs",

    "lib": ["es2015", "DOM"],//

    // ...

  }

}

refs

https://stackoverflow.com/questions/49699067/property-has-no-initializer-and-is-not-definitely-assigned-in-the-construc

https://stackoverflow.com/questions/54104187/typescript-complain-has-no-initializer-and-is-not-definitely-assigned-in-the-co/54104796

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