Home/ Questions/How to solve the issue expected an assignment or function call and instead saw an expression?
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Daryl Schmidt
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Asked: 2022-06-30T12:54:40+00:00 In:

How to solve the issue expected an assignment or function call and instead saw an expression?

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I got this message “expected an assignment or function call and instead saw an expression” when I run the code bellow:

App.js

const App = props => {
const result = ['a', 'b', 'c'].map(el => {
// ⛔️ Expected an assignment or function call and instead saw an expression. eslint no-unused-expressions
el + '100';
});

return <div>hello world</div>;
};

const mapStateToProps = (state) => {
// ⛔️ Expected an assignment or function call and instead saw an expression. eslint no-unused-expressions
todos: ['walk the dog', 'buy groceries']
}

export default App;

I don’t know where I went wrong, looking forward to the answer. Thanks for everyone’s help.

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1 Answer

  1. Best Answer
    Expert

    The cause: The Array.map() method in the App component is where the error is generated. You failed to supply a value from the mapStateToProps function, which is the problem.

    Solution:  Either an explicit return statement or the use of an arrow function to indirectly return a value will fix the problem. The error can be fixed with an explicit return, as seen in the following example.

    App.js
const App = props => {
const result = ['a', 'b', 'c'].map(el => {
return el + '100'; // 👈️ using explicit return
});

console.log(result);

return <div>hello world</div>;
};

const mapStateToProps = state => {
return {todos: ['walk the dog', 'buy groceries']}; // 👈️ using explicit return
};

export default App;

     

    Follow the article below to understand more

    👇️ Resolve error: “Expected an assignment or function call and instead saw an expression”

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