#no-cond-assign

#Configuration

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

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'no-cond-assign': 'error',
    },
  },
]);

#Rule Details

Disallows assignment operators in test expressions (if, while, do-while, for, and ternary). Assignments in tests are frequently a typo where the developer meant to use a comparison operator (===) instead of an assignment operator (=).

In the default "except-parens" mode, a top-level assignment is allowed when extra parentheses signal that it is intentional. A ternary test needs two explicit pairs because, unlike a statement test, it has no grammar parentheses. In "always" mode, assignments descended from a test expression are flagged, stopping at nested function boundaries. An assignment in a ternary branch is not part of that ternary's test, so it is allowed when the ternary is outside another conditional test. If the whole ternary is itself an outer test, "always" mode reports the assignment against that outer conditional. Assignments in statement bodies are allowed in both modes.

Examples of incorrect code for this rule:

if (x = 0) {
}

while (x = next()) {}

var result = (x = next()) ? y : z;

Examples of correct code for this rule:

if (x === 0) {
}

while ((x = next())) {} // extra parens signal intent

if (x === 0 || (y = getValue())) {
}

for (; (a = b); ) {}

var result = ((x = next())) ? y : z;

var branchResult = x ? (y = 1) : z; // assignment is in a branch, not the test

#Original Documentation

• ESLint: no-cond-assign
• Source code