[typescript] Typescript: TS7006: Parameter 'xxx' implicitly has an 'any' type

In testing my UserRouter, I am using a json file

data.json

[
  {
    "id": 1,
    "name": "Luke Cage",
    "aliases": ["Carl Lucas", "Power Man", "Mr. Bulletproof", "Hero for Hire"],
    "occupation": "bartender",
    "gender": "male",
    "height": {
      "ft": 6,
      "in": 3
    },
    "hair": "bald",
    "eyes": "brown",
    "powers": [
      "strength",
      "durability",
      "healing"
    ]
  },
  {
  ...
  }
]

Building my app, I get the following TS error

ERROR in ...../UserRouter.ts
(30,27): error TS7006: Parameter 'user' implicitly has an 'any' type.

UserRouter.ts

import {Router, Request, Response, NextFunction} from 'express';
const Users = require('../data');

export class UserRouter {
  router: Router;

  constructor() {
  ...
  }

  /**
   * GET one User by id
   */
  public getOne(req: Request, res: Response, _next: NextFunction) {
    let query = parseInt(req.params.id);
 /*[30]->*/let user = Users.find(user => user.id === query);
    if (user) {
      res.status(200)
        .send({
          message: 'Success',
          status: res.status,
          user
        });
    }
    else {
      res.status(404)
        .send({
          message: 'No User found with the given id.',
          status: res.status
        });
    }
  }


}

const userRouter = new UserRouter().router;
export default userRouter;

I encounted this error and found that it was because the "strict" parameter was set to true in the tsconfig.json file. Just set it "false" (obviously). In my case I had generated the tsconfig file from the cmd prompt and simply missed the "strict" parameter, which was located further down in the file.

In your tsconfig.json file set the parameter "noImplicitAny": false under compilerOptions to get rid of this error.

Very sort cut and effective solution is below:-

Add the below rule in your tsconfig.json file:-

"noImplicitAny": false

Then restart your project.

go to tsconfig.json and comment the line the //strict:true this worked for me

Minimal error reproduction

export const users = require('../data'); // presumes @types/node are installed
const foundUser = users.find(user => user.id === 42); 
// error: Parameter 'user' implicitly has an 'any' type.ts(7006)

Recommended solution: --resolveJsonModule

The simplest way for your case is to use --resolveJsonModule compiler option:

import users from "./data.json" // `import` instead of `require`
const foundUser = users.find(user => user.id === 42); // user is strongly typed, no `any`!

---

There are some alternatives for other cases than static JSON import.

Option 1: Explicit user type (simple, no checks)

type User = { id: number; name: string /* and others */ }
const foundUser = users.find((user: User) => user.id === 42)

Option 2: Type guards (middleground)

Type guards are a good middleground between simplicity and strong types:

function isUserArray(maybeUserArr: any): maybeUserArr is Array<User> {
  return Array.isArray(maybeUserArr) && maybeUserArr.every(isUser)
}

function isUser(user: any): user is User {
  return "id" in user && "name" in user
}

if (isUserArray(users)) {
  const foundUser = users.find((user) => user.id === 42)
}

You can even switch to assertion functions (TS 3.7+) to get rid of if and throw an error instead.

function assertIsUserArray(maybeUserArr: any): asserts maybeUserArr is Array<User> {
  if(!isUserArray(maybeUserArr)) throw Error("wrong json type")
}

assertIsUserArray(users)
const foundUser = users.find((user) => user.id === 42) // works

Option 3: Runtime type system library (sophisticated)

A runtime type check library like io-ts or ts-runtime can be integrated for more complex cases.

---

Not recommended solutions

noImplicitAny: false undermines many useful checks of the type system:

function add(s1, s2) { // s1,s2 implicitely get `any` type
  return s1 * s2 // `any` type allows string multiplication and all sorts of types :(
}
add("foo", 42)

Also better provide an explicit User type for user. This will avoid propagating any to inner layer types. Instead typing and validating is kept in the JSON processing code of the outer API layer.

if you get an error as Parameter 'element' implicitly has an 'any' type.Vetur(7006) in vueJs

with the error:

 exportColumns.forEach(element=> {
      if (element.command !== undefined) {
        let d = element.command.findIndex(x => x.name === "destroy");

you can fixed it by defining thoes variables as any as follow.

corrected code:

exportColumns.forEach((element: any) => {
      if (element.command !== undefined) {
        let d = element.command.findIndex((x: any) => x.name === "destroy");