disallow ternary operators when simpler alternatives exist (no-unneeded-ternary)
The --fix
option on the command line can automatically fix some of the problems reported by this rule.
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
Version
This rule was introduced in ESLint 0.21.0.