no-dupe-class-members.md

title	rule_type	handled_by_typescript
no-dupe-class-members	problem	true

If there are declarations of the same name in class members, the last declaration overwrites other declarations silently. It can cause unexpected behaviors.

/*eslint-env es6*/

class Foo {
  bar() { console.log("hello"); }
  bar() { console.log("goodbye"); }
}

var foo = new Foo();
foo.bar(); // goodbye

Rule Details

This rule is aimed to flag the use of duplicate names in class members.

Examples

Examples of incorrect code for this rule:

::: incorrect

/*eslint no-dupe-class-members: "error"*/

class Foo {
  bar() { }
  bar() { }
}

class Foo {
  bar() { }
  get bar() { }
}

class Foo {
  bar;
  bar;
}

class Foo {
  bar;
  bar() { }
}

class Foo {
  static bar() { }
  static bar() { }
}

:::

Examples of correct code for this rule:

::: correct

/*eslint no-dupe-class-members: "error"*/

class Foo {
  bar() { }
  qux() { }
}

class Foo {
  get bar() { }
  set bar(value) { }
}

class Foo {
  bar;
  qux;
}

class Foo {
  bar;
  qux() { }
}

class Foo {
  static bar() { }
  bar() { }
}

:::

When Not To Use It

This rule should not be used in ES3/5 environments.

In ES2015 (ES6) or later, if you don't want to be notified about duplicate names in class members, you can safely disable this rule.