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Disallow arrow functions where they could be confused with comparisons (no-confusing-arrow)

The --fix option on the command line can automatically fix some of the problems reported by this rule.

Arrow functions (=>) are similar in syntax to some comparison operators (>, <, <=, and >=). This rule warns against using the arrow function syntax in places where it could be confused with a comparison operator.

Here's an example where the usage of => could be confusing:

// The intent is not clear
var x = a => 1?2 : 3;
// Did the author mean this
var x = function (a) { return 1?2 : 3 };
// Or this
var x = a <= 1?2 : 3;

Rule Details

Examples of incorrect code for this rule:

/*eslint no-confusing-arrow: "error"*/
/*eslint-env es6*/

var x = a => 1?2 : 3;
var x = (a) => 1?2 : 3;

Examples of correct code for this rule:

/*eslint no-confusing-arrow: "error"*/
/*eslint-env es6*/

var x = a => (1?2 : 3);
var x = (a) => (1?2 : 3);
var x = a => { return 1?2 : 3; };
var x = (a) => { return 1?2 : 3; };

Options

This rule accepts a single options argument with the following defaults:

{
    "rules": {
        "no-confusing-arrow": ["error", {"allowParens": true}]
    }
}

allowParens is a boolean setting that can be true(default) or false:

1. true relaxes the rule and accepts parenthesis as a valid "confusion-preventing" syntax.
2. false warns even if the expression is wrapped in parenthesis

Examples of incorrect code for this rule with the {"allowParens": false} option:

/*eslint no-confusing-arrow: ["error", {"allowParens": false}]*/
/*eslint-env es6*/
var x = a => (1?2 : 3);
var x = (a) => (1?2 : 3);

Related Rules

• no-constant-condition
• arrow-parens

Version

This rule was introduced in ESLint 2.0.0-alpha-2.

Resources

• Rule source
• Documentation source