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When we don’t type the properties of a function or class component or forget to install typings for React, React.js will give an error “Parameter 'props' implicitly has an 'any' type”. To fix the error, explicitly set propsthe type of the object in the component.

The first thing we should make sure is that we have React typings installed. package.jsonOpen a terminal in the root directory of your project (where your files are located) and run the following command.

# 👇️ 使用 NPM
$ npm install --save-dev @types/react @types/react-dom

# ----------------------------------------------

# 👇️ 使用 YARN
$ yarn add @types/react @types/react-dom --dev

Try restarting the IDE and the service.

If that doesn't help, it's possible that you forgot to explicitly type a function or class component props. Here's sample code that produces the above error.

// ⛔️ Parameter 'props' implicitly has an 'any' type.ts(7006)
function Person(props) {
  return (
    <div>
      <h2>{props.name}</h2>
      <h2>{props.age}</h2>
      <h2>{props.country}</h2>
    </div>
  );
}

function App() {
  return (
    <div>
      <Person name="jiyik.com" age={30} country="China" />
    </div>
  );
}

export default App;

The problem with the above code snippet is that we haven't set a type for the function component props.

To fix this error, we have to explicitly enter propsthe parameters.

interface PersonProps {
  name: string;
  age: number;
  country: string;
  children?: React.ReactNode;
}

function Person(props: PersonProps) {
  return (
    <div>
      <h2>{props.name}</h2>
      <h2>{props.age}</h2>
      <h2>{props.country}</h2>
    </div>
  );
}

function App() {
  return (
    <div>
      <Person name="jiyik.com" age={30} country="China" />
    </div>
  );
}

export default App;

We defined an interface to explicitly input the props of the component, which resolved the error.

We don't have to set the children property, but we would have to do so if we passed children to a component.

If we don't want to explicitly type propsthe object for our component, we can use anythe type.

// 👇️ 设置为 any 类型
function Person(props: any) {
  return (
    <div>
      <h2>{props.name}</h2>
      <h2>{props.age}</h2>
      <h2>{props.country}</h2>
    </div>
  );
}

function App() {
  return (
    <div>
      <Person name="jiyik.com" age={30} country="China" />
    </div>
  );
}

export default App;

anyThe type effectively turns off type checking, so we are able to propspass the to the component and access properties on the object without getting any type checking errors.

If we have a class component, use generics to type its props and state.

import React from 'react';

interface PersonProps {
  name: string;
  age: number;
  country: string;
  children?: React.ReactNode;
}


interface PersonState {
  value: string;
}

// 👇️ React.Component<PropsType, StateType>
class Person extends React.Component<PersonProps, PersonState> {
  render() {
    return (
      <div>
        <h2>{this.props.name}</h2>
        <h2>{this.props.age}</h2>
        <h2>{this.props.country}</h2>
      </div>
    );
  }
}

export default function App() {
  return (
    <div>
      <Person name="James" age={30} country="Australia" />
    </div>
  );
}

We explicitly provided types for the component's props and state, thus resolving the error.

If you don't want to explicitly type your component's props and state, you can use anytypes.

import React from 'react';

// 👇️ 对 props 和 state 禁用类型检查
class App extends React.Component<any, any> {
  constructor(props: any) {
    super(props);

    this.state = {value: ''};
  }

  handleChange = (event: any) => {
    this.setState({value: event.target.value});
  };

  render() {
    return (
      <div>
        <form>
          <input
            onChange={this.handleChange}
            type="text"
            value={this.state.value}
          />
          <button type="submit">Submit</button>
        </form>
      </div>
    );
  }
}

export default App;

We used the type when typing the props and state objects any, which effectively turned off type checking.

Now we can access any property on the this.props and this.state objects without getting type checking errors.

If the error is not resolved, try deleting the node_modules and package-lock.json (not package.json) files, re-running npm installand restarting the IDE.

# 👇️ 删除 node_modules 和 package-lock.json
$ rm -rf node_modules
$ rm -f package-lock.json

# 👇️ 清除 npm 缓存
$ npm cache clean --force

$ npm install

If the error persists, make sure to restart the IDE and the development server. VSCode often crashes and sometimes restarting can fix the problem.