objectHasOwns

Prefer Object.hasOwn() over Object.prototype.hasOwnProperty.call() for checking own properties.

✅ This rule is included in the ts stylistic and stylisticStrict presets.

Object.hasOwn() is the modern, recommended way to check if an object has a property as its own property (not inherited from the prototype chain). It provides a safer and more convenient alternative to older patterns like Object.prototype.hasOwnProperty.call() or calling hasOwnProperty() directly on objects.

Using Object.hasOwn() avoids potential issues with objects that don’t inherit from Object.prototype, such as objects created with Object.create(null) and objects that have overridden the hasOwnProperty method.

const 
const hasKey: any
hasKey = 
const obj: any
obj.
any
hasOwnProperty("key");

if (
const obj: any
obj.
any
hasOwnProperty("prop")) {
  
var console: Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:

A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
@see ― source
console.
Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
@since ― v0.1.100
log("Has property");
}

const 
const result: boolean
result = 
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.prototype: Object
A reference to the prototype for a class of objects.
prototype.
Object.hasOwnProperty(v: PropertyKey): boolean
Determines whether an object has a property with the specified name.
@param ― v A property name.
hasOwnProperty.
CallableFunction.call<any, [string], boolean>(this: (this: any, args_0: string) => boolean, thisArg: any, args_0: string): boolean
Calls the function with the specified object as the this value and the specified rest arguments as the arguments.
@param ― thisArg The object to be used as the this object.
@param ― args Argument values to be passed to the function.
call(
const obj: any
obj, "key");

const 
const exists: boolean
exists = {}.
Object.hasOwnProperty(v: PropertyKey): boolean
Determines whether an object has a property with the specified name.
@param ― v A property name.
hasOwnProperty.
CallableFunction.call<any, [string], boolean>(this: (this: any, args_0: string) => boolean, thisArg: any, args_0: string): boolean
Calls the function with the specified object as the this value and the specified rest arguments as the arguments.
@param ― thisArg The object to be used as the this object.
@param ― args Argument values to be passed to the function.
call(
const obj: any
obj, "prop");

const 
const hasKey: boolean
hasKey = 
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.hasOwn(o: object, v: PropertyKey): boolean
Determines whether an object has a property with the specified name.
@param ― o An object.
@param ― v A property name.
hasOwn(
const obj: any
obj, "key");

if (
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.hasOwn(o: object, v: PropertyKey): boolean
Determines whether an object has a property with the specified name.
@param ― o An object.
@param ― v A property name.
hasOwn(
const obj: any
obj, "prop")) {
  
var console: Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:

A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
@see ― source
console.
Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
@since ― v0.1.100
log("Has property");
}

const 
const result: boolean
result = 
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.hasOwn(o: object, v: PropertyKey): boolean
Determines whether an object has a property with the specified name.
@param ― o An object.
@param ― v A property name.
hasOwn(
const obj: any
obj, "key");

const 
const exists: boolean
exists = 
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.hasOwn(o: object, v: PropertyKey): boolean
Determines whether an object has a property with the specified name.
@param ― o An object.
@param ― v A property name.
hasOwn(
const obj: any
obj, "prop");

Options

This rule is not configurable.

When Not To Use It

If you need to support JavaScript environments that don’t have Object.hasOwn() (pre-ES2022), you might need to disable this rule or use a polyfill. Object.hasOwn() is supported in Node.js 16.9.0+ and all modern browsers.

For projects with a large existing codebase using the older patterns, and projects where hasOwn and/or hasOwnProperty are overridden with custom semantics, this rule might not be applicable.

Equivalents in Other Linters

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objectHasOwns

Examples

Options

When Not To Use It

Further Reading

Equivalents in Other Linters