how to fix TypeScript error 'this' implicitly has type 'any' All In One

'this' implicitly has type 'any' because it does not have a type annotation.ts(2683)

'this' 隐式具有类型 'any' 因为它没有类型注释。

errors ❌

const nums = [1, 2, 3];
nums.myForEach(function(a, b, c, thisObj) {
  console.log(`a, b, c =`, a, b, c);
  console.log(`thisObj =`, thisObj);
  console.log(`this = `, this);
});

solutions

function(this:any, ...) 👍 推荐方式

✅ just add this: any as the ES5 function's first argument.

只需要把 this:any 添加到函数的第一个参数位置即可，这不会影响后面正常参数的传入顺序！

const nums = [1, 2, 3];
nums.myForEach(function(this: any, a, b, c, thisObj) {
  // A 'this' parameter must be the first parameter.ts(2680) ✅
  console.log(`a, b, c =`, a, b, c);
  console.log(`thisObj =`, thisObj);
  console.log(`this = `, this);
});

"noImplicitThis": false, 禁用错误提示 👎 不推荐

tsconfig.json

{
  "compilerOptions": {
    // "target": "ES2022",
    // "target": "ES2020",
    "target": "ESNext",
    // "module": "NodeNext",
    "module": "ESNext",
    "lib": [
      "ES2015",
      "ES2016",
      "ES2017",
      "ES2018",
      "ES2019",
      "ES2020",
      // "ES2021",
      // "ES2022",
      "ESNext",
      "dom",
      "dom.iterable"
    ],
    "downlevelIteration": false,
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "sourceMap": true,
    "sourceRoot": "./src",
    "allowJs": true,
    // Generate d.ts files ✅
    "declaration": true,
    "checkJs": false,
    "noImplicitAny": false,
    "baseUrl": "./src",
    "locale": "zh-CN",
    "noImplicitReturns": true,
    // fix: https://github.com/xgqfrms/learn-typescript-by-practice/issues/29
    "noImplicitThis": false,
    // https://github.com/xgqfrms/vscode/issues/67
    // "allowImportingTsExtensions": true,
    // error TS5023: Unknown compiler option 'allowImportingTsExtensions'. ❌
    // "noEmit": true,
    // Option 'allowImportingTsExtensions' can only be used when either 'noEmit' or 'emitDeclarationOnly' is set.ts
    "incremental": false
  },
  "type": "module",
  "include": [
    // include folder ✅
    "src/**/*",
    // "js-solutions/**/*",
    "test/**/*"
  ],
  "exclude": [
    "node_modules",
    "build",
    "js-solutions/**/*",
    "data-structures/**/*",
    "000-xyz/**/*",
    "test/**/*.spec.ts"
  ]
}