TypeScript Errors All In One

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

1. 👍

class CC {
  foo: number;
  bar = "hello";
  baz: boolean | undefined;
  constructor() {
    this.foo = 42;
  }
}

2. 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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