've setup eslint & eslint-plugin-react.

When I run ESLint, the linter returns no-unused-vars errors for each React ponent.

I'm assuming it's not recognizing that I'm using JSX or React syntax. Any ideas?

this my code--

've setup eslint & eslint-plugin-react.

When I run ESLint, the linter returns no-unused-vars errors for each React ponent.

I'm assuming it's not recognizing that I'm using JSX or React syntax. Any ideas?

this my code--

• javascript
• reactjs
• eslint

Share Improve this question Follow edited Jun 20, 2020 at 9:12 CommunityBot 111 silver badge asked Sep 9, 2018 at 12:33 aliali 15111 gold badge22 silver badges55 bronze badges 1

• 4 Always paste real code, never images of code. – connexo Commented Sep 9, 2018 at 12:37

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3 Answers 3

Sorted by: Reset to default 4

In your codeblock

users.forEach((user, index) => { ... }) 
                     ^^^^^

you never use the parameter index, rendering it useless. That why ESLint plains - rightfully.

Instead go

users.forEach((user) => { ... }) 

As another answer already explains, no-unused-vars rule triggers linter error because index parameter isn't in use. It can be omitted:

users.forEach(user => {
  /* ... */
});

If for some reason a parameter is temporarily not in use but is expected to be used later, or it's needed for proper function arity (this is not the case for forEach), it can be marked as unused (conventionally, underscored parameters treated as such):

users.forEach((user, _index) => {
  /* ... */
});

Expected parentheses around arrow function argument linter error means that it was configured to enforce optional parentheses in arrow functions with arrow-parens rule. This can be changed by either disabling this rule or adding parentheses:

users.forEach((user) => {
  /* ... */
});

The latter option may be preferred because enforced arrow parentheses are more consistent.

 handleSelectAll = () => {
    const { users } = this.props.users
    this.setState((prevState) => {
      const newState = { ...prevState }
      newState.selects = []
      users.forEach(user => {
        newState.selects.push(!prevState.selectedAll)
      });
      newState.selectedAll = !prevState.selectedAll
      return newState
    })
  }

"message: 'Expected parentheses around arrow function argument. (arrow-parens)"