eslint/no-multi-assign Style

What it does

Disallow use of chained assignment expressions.

Why is this bad?

Chaining the assignment of variables can lead to unexpected results and be difficult to read.

(function() {
  const foo = bar = 0; // Did you mean `foo = bar == 0`?
  bar = 1; // This will not fail since `bar` is not constant.
})();
console.log(bar); // This will output 1 since `bar` is not scoped.

Examples

Examples of incorrect code for this rule:

var a = b = c = 5;

const foo = bar = "baz";

let d = e = f;

class Foo {
  a = b = 10;
}

a = b = "quux";

Examples of correct code for this rule:

var a = 5;
var b = 5;
var c = 5;

const foo = "baz";
const bar = "baz";

let d = c;
let e = c;

class Foo {
  a = 10;
  b = 10;
}

a = "quux";
b = "quux";

Configuration

This rule accepts a configuration object with the following properties:

ignoreNonDeclaration

type: boolean

default: false

When set to true, the rule allows chains that don't include initializing a variable in a declaration or initializing a class field.

Examples of correct code for this option set to true:

let a;
let b;
a = b = "baz";

const x = {};
const y = {};
x.one = y.one = 1;

Examples of incorrect code for this option set to true:

let a = b = "baz";

const foo = bar = 1;

class Foo {
  a = b = 10;
}

How to use

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

CLI

oxlint --deny no-multi-assign

Config (.oxlintrc.json)

{
  "rules": {
    "no-multi-assign": "error"
  }
}

References

• Rule Source