noDuplicateObjectKeys (JavaScript)

Summary

Rule available since: v1.0.0
Diagnostic Category: lint/suspicious/noDuplicateObjectKeys
This rule is recommended, meaning it is enabled by default.
This rule has an unsafe fix.
The default severity of this rule is error.
Sources:
- Same as no-dupe-keys

How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "suspicious": {
5
        "noDuplicateObjectKeys": "error"
6
      }
7
    }
8
  }
9
}

Description

Disallow two keys with the same name inside objects.

If an object property with the same name is defined multiple times (except when combining a getter with a setter), only the last definition makes it into the object and previous definitions are ignored, which is likely a mistake.

Examples

Invalid

1
const obj = {
2
     a: 1,
3
     a: 2,
4
}

code-block.js:2:5 lint/suspicious/noDuplicateObjectKeys  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This property is later overwritten by an object member with the same name.
  
    1 │ const obj = {
  > 2 │    	a: 1,
      │    	^^^^
    3 │    	a: 2,
    4 │ }
  
  ℹ Overwritten with this property.
  
    1 │ const obj = {
    2 │    	a: 1,
  > 3 │    	a: 2,
      │    	^^^^
    4 │ }
    5 │ 
  
  ℹ If an object property with the same name is defined multiple times (except when combining a getter with a setter), only the last definition makes it into the object and previous definitions are ignored.
  
  ℹ Unsafe fix: Remove this property.
  
    1 1 │   const obj = {
    2   │ - ···→ a:·1,
    3 2 │      	a: 2,
    4 3 │   }

1
const obj = {
2
     set a(v) {},
3
     a: 2,
4
}

code-block.js:2:5 lint/suspicious/noDuplicateObjectKeys  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This setter is later overwritten by an object member with the same name.
  
    1 │ const obj = {
  > 2 │    	set a(v) {},
      │    	^^^^^^^^^^^
    3 │    	a: 2,
    4 │ }
  
  ℹ Overwritten with this property.
  
    1 │ const obj = {
    2 │    	set a(v) {},
  > 3 │    	a: 2,
      │    	^^^^
    4 │ }
    5 │ 
  
  ℹ If an object property with the same name is defined multiple times (except when combining a getter with a setter), only the last definition makes it into the object and previous definitions are ignored.
  
  ℹ Unsafe fix: Remove this setter.
  
    1 1 │   const obj = {
    2   │ - ···→ set·a(v)·{},
    3 2 │      	a: 2,
    4 3 │   }

Valid

1
const obj = {
2
     a: 1,
3
     b: 2,
4
}

1
const obj = {
2
     get a() { return 1; },
3
     set a(v) {},
4
}