prefer-object-has-own

Disallow use of Object.prototype.hasOwnProperty.call() and prefer use of Object.hasOwn()

It is very common to write code like:

if (Object.prototype.hasOwnProperty.call(object, "foo")) {
  console.log("has property foo");
}
1
2
3

This is a common practice because methods on Object.prototype can sometimes be unavailable or redefined (see the no-prototype-builtins rule).

Introduced in ES2022, Object.hasOwn() is a shorter alternative to Object.prototype.hasOwnProperty.call():

if (Object.hasOwn(object, "foo")) {
  console.log("has property foo")
}
1
2
3

Rule Details

Examples of incorrect code for this rule:

/*eslint prefer-object-has-own: "error"*/

Object.prototype.hasOwnProperty.call(obj, "a");

Object.hasOwnProperty.call(obj, "a");

({}).hasOwnProperty.call(obj, "a");

const hasProperty = Object.prototype.hasOwnProperty.call(object, property);
1
2
3
4
5
6
7
8
9

Examples of correct code for this rule:

/*eslint prefer-object-has-own: "error"*/

Object.hasOwn(obj, "a");

const hasProperty = Object.hasOwn(object, property);
1
2
3
4
5

When Not To Use It

This rule should not be used unless ES2022 is supported in your codebase.

Version

This rule was introduced in ESLint v8.5.0.

Further Reading

Object.hasOwn() - JavaScript | MDN
developer.mozilla.org

Resources

• Rule source
• Tests source