noClassAssign

JavaScript (and super languages)

Summary

• Rule available since: v1.0.0
• Diagnostic Category: lint/suspicious/noClassAssign
• This rule is recommended, which means is enabled by default.
• This rule doesn’t have a fix.
• The default severity of this rule is error.
• Sources:
  • Same as no-class-assign

How to configure

biome.json

{
  "linter": {
    "rules": {
      "suspicious": {
        "noClassAssign": "error"
      }
    }
  }
}

Description

Disallow reassigning class members.

A class declaration creates a variable that we can modify, however, the modification is a mistake in most cases.

Examples

Invalid

class A {}
A = 0;

code-block.js:2:1 lint/suspicious/noClassAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ ‘A’ is a class.
  
    1 │ class A {}
  > 2 │ A = 0;
      │ ^
    3 │ 
  
  ℹ ‘A’ is defined here.
  
  > 1 │ class A {}
      │       ^
    2 │ A = 0;
    3 │ 
  

A = 0;
class A {}

code-block.js:1:1 lint/suspicious/noClassAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ ‘A’ is a class.
  
  > 1 │ A = 0;
      │ ^
    2 │ class A {}
    3 │ 
  
  ℹ ‘A’ is defined here.
  
    1 │ A = 0;
  > 2 │ class A {}
      │       ^
    3 │ 
  

class A {
  b() {
    A = 0;
  }
}

code-block.js:3:3 lint/suspicious/noClassAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ ‘A’ is a class.
  
    1 │ class A {
    2 │ 	b() {
  > 3 │ 		A = 0;
      │ 		^
    4 │ 	}
    5 │ }
  
  ℹ ‘A’ is defined here.
  
  > 1 │ class A {
      │       ^
    2 │ 	b() {
    3 │ 		A = 0;
  

let A = class A {
  b() {
    A = 0;
    // `let A` is shadowed by the class name.
  }
}

code-block.js:3:3 lint/suspicious/noClassAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ ‘A’ is a class.
  
    1 │ let A = class A {
    2 │ 	b() {
  > 3 │ 		A = 0;
      │ 		^
    4 │ 		// `let A` is shadowed by the class name.
    5 │ 	}
  
  ℹ ‘A’ is defined here.
  
  > 1 │ let A = class A {
      │               ^
    2 │ 	b() {
    3 │ 		A = 0;
  

Valid

let A = class A {}
A = 0; // A is a variable.

let A = class {
    b() {
        A = 0; // A is a variable.
    }
}

class A {
  b(A) {
    A = 0; // A is a parameter.
  }
}

Related links

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• Test Cases