#restrict-plus-operands

#Configuration

import { defineConfig, ts } from '@rslint/core';

export default defineConfig([
  ts.configs.recommended,
  {
    rules: {
      '@typescript-eslint/restrict-plus-operands': 'error',
    },
  },
]);

#Rule Details

Require both operands of addition to be the same type and be bigint, number, or string. The + operator in TypeScript can be used for both addition and string concatenation. This rule ensures that operands of + are both numbers, both bigints, or both strings, preventing accidental implicit type coercions that can lead to unexpected results (e.g., "1" + 2 becoming "12" instead of 3).

Examples of incorrect code for this rule:

const result = 1 + '2';
const bad = 1n + 2;
const invalid = {} + [];

Examples of correct code for this rule:

const sum = 1 + 2;
const concat = 'a' + 'b';
const bigSum = 1n + 2n;
const explicit = String(1) + '2';

#Original Documentation

• typescript-eslint: restrict-plus-operands
• Source code