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. Even if the arguments of the arrow function are wrapped with parens, this rule still warns about it unless allowParens is set to true.

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

Examples of correct code for this rule:

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

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": false}]
    }
}

allowParens is a boolean setting that can be true 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 correct code for this rule with the {"allowParens": true} option:

/*eslint no-confusing-arrow: ["error", {"allowParens": true}]*/
/*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