eslint/no-sequences Restriction

What it does

Disallows the use of the comma operator.

Why is this bad?

The comma operator evaluates each of its operands (from left to right) and returns the value of the last operand. However, this frequently obscures side effects, and its use is often an accident.

Options

• allowInParentheses (default: true): If set to false, disallows the comma operator even when wrapped in parentheses.

Examples

Examples of incorrect code for this rule:

foo = doSomething(), val;

0, eval("doSomething();");

// Arrow function body needs double parentheses
const fn = () => (doSomething(), val);

// with allowInParentheses: false
foo = (doSomething(), val);

Examples of correct code for this rule:

foo = (doSomething(), val);

(0, eval)("doSomething();");

// Single extra parentheses is enough for conditions
do {} while ((doSomething(), !!test));

for (i = 0, j = 10; i < j; i++, j--) {}

// Arrow function body needs double parentheses
const fn = () => ((doSomething(), val));

Configuration

This rule accepts a configuration object with the following properties:

allowInParentheses

type: boolean

default: true

If this option is set to false, this rule disallows the comma operator even when the expression sequence is explicitly wrapped in parentheses. Default is true.

How to use

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)

{
    "rules": {
        "no-sequences": "error"
    }
}

CLI

oxlint --deny no-sequences

References

• Rule Source