prefer-class-properties

Moves simple literal defaults out of the constructor and into class fields.

Rule details Suggestion

By default, this rule reports this.property = value assignments inside constructors when value is known at class definition time. That includes primitive literals, literal arrays, and object literals without spreads or computed properties.

The rule only checks constructor assignments to this properties. If the value depends on constructor parameters or runtime work, it is left alone.

There is also a reverse mode

Set the rule to "never" if you want to ban instance field declarations and keep initialization in the constructor instead.

Examples

Incorrect

class User {
  constructor() {
    this.name = "Unknown";
    this.age = 0;
    this.flags = [true, false];
  }
}

Correct

class User {
  name = "Unknown";
  age = 0;
  flags = [true, false];
}

class Service {
  constructor(options: Options) {
    this.options = options;
  }
}

Options

Option	Default	What it does
"always"	yes	Reports constructor assignments of simple literal values and prefers class fields.
"never"	no	Reports non-static class property declarations and prefers constructor initialization.

eslint.config.js

import ceaseNonsense from "eslint-plugin-cease-nonsense";

export default [
  {
    plugins: {
      "cease-nonsense": ceaseNonsense,
    },
    rules: {
      "cease-nonsense/prefer-class-properties": ["error", "never"],
    },
  },
];

Related rules

no-async-constructor Keeps constructors focused on setup

no-instance-methods-without-this Moves class code to a better place when `this` is not used