no-unneeded-ternary.md

disallow ternary operators when simpler alternatives exist (no-unneeded-ternary)

It's a common mistake in JavaScript to use a conditional expression to select between two Boolean values instead of using ! to convert the test to a Boolean. Here are some examples:

// Bad
var isYes = answer === 1 ? true : false;

// Good
var isYes = answer === 1;


// Bad
var isNo = answer === 1 ? false : true;

// Good
var isNo = answer !== 1;

Another common mistake is using a single variable as both the conditional test and the consequent. In such cases, the logical OR can be used to provide the same functionality. Here is an example:

// Bad
var foo = bar ? bar : 1;

// Good
var foo = bar || 1;

Rule Details

This rule disallow ternary operators when simpler alternatives exist.

Examples of incorrect code for this rule:

/*eslint no-unneeded-ternary: "error"*/

var a = x === 2 ? true : false;

var a = x ? true : false;

Examples of correct code for this rule:

/*eslint no-unneeded-ternary: "error"*/

var a = x === 2 ? "Yes" : "No";

var a = x !== false;

var a = x ? "Yes" : "No";

var a = x ? y : x;

var a = x ? x : 1;

Options

This rule has an object option:

• "defaultAssignment": true (default) allows the conditional expression as a default assignment pattern
• "defaultAssignment": false disallows the conditional expression as a default assignment pattern

defaultAssignment

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

/*eslint no-unneeded-ternary: ["error", { "defaultAssignment": false }]*/

var a = x ? x : 1;

When Not To Use It

You can turn this rule off if you are not concerned with unnecessary complexity in conditional expressions.

Related Rules

• no-ternary
• no-nested-ternary