This rule was deprecated in ESLint v3.9.0 and will not be replaced. The original intent of this rule now seems misguided as we have come to understand that Reflect methods are not actually intended to replace the Object counterparts the rule suggests, but rather exist as low-level primitives to be used with proxies in order to replicate the default behavior of various previously existing functionality.
The ES6 Reflect API comes with a handful of methods which somewhat deprecate methods on old constructors:
Reflect.apply effectively deprecates Function.prototype.apply and Function.prototype.call
Reflect.deleteProperty effectively deprecates the delete keyword
Reflect.getOwnPropertyDescriptor effectively deprecates Object.getOwnPropertyDescriptor
Reflect.getPrototypeOf effectively deprecates Object.getPrototypeOf
Reflect.setPrototypeOf effectively deprecates Object.setPrototypeOf
Reflect.preventExtensions effectively deprecates Object.preventExtensions
The prefer-reflect rule will flag usage of any older method, suggesting to instead use the newer Reflect version.
"prefer-reflect": [<enabled>, { "exceptions": [<...exceptions>] }]
The exceptions option allows you to pass an array of methods names you'd like to continue to use in the old style.
For example if you wish to use all Reflect methods, except for Function.prototype.apply then your config would look like prefer-reflect: [2, { "exceptions": ["apply"] }].
If you want to use Reflect methods, but keep using the delete keyword, then your config would look like prefer-reflect: [2, { "exceptions": ["delete"] }].
These can be combined as much as you like. To make all methods exceptions (thereby rendering this rule useless), use prefer-reflect: [2, { "exceptions": ["apply", "call", "defineProperty", "getOwnPropertyDescriptor", "getPrototypeOf", "setPrototypeOf", "isExtensible", "getOwnPropertyNames", "preventExtensions", "delete"] }]
Deprecates Function.prototype.apply() and Function.prototype.call()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
myFunction.apply(undefined, args);
myFunction.apply(null, args);
obj.myMethod.apply(obj, args);
obj.myMethod.apply(other, args);
myFunction.call(undefined, arg);
myFunction.call(null, arg);
obj.myMethod.call(obj, arg);
obj.myMethod.call(other, arg);
Examples of correct code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Reflect.apply(myFunction, undefined, args);
Reflect.apply(myFunction, null, args);
Reflect.apply(obj.myMethod, obj, args);
Reflect.apply(obj.myMethod, other, args);
Reflect.apply(myFunction, undefined, [arg]);
Reflect.apply(myFunction, null, [arg]);
Reflect.apply(obj.myMethod, obj, [arg]);
Reflect.apply(obj.myMethod, other, [arg]);
Examples of correct code for this rule with the { "exceptions": ["apply"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["apply"] }]*/
// in addition to Reflect.apply(...):
myFunction.apply(undefined, args);
myFunction.apply(null, args);
obj.myMethod.apply(obj, args);
obj.myMethod.apply(other, args);
Examples of correct code for this rule with the { "exceptions": ["call"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["call"] }]*/
// in addition to Reflect.apply(...):
myFunction.call(undefined, arg);
myFunction.call(null, arg);
obj.myMethod.call(obj, arg);
obj.myMethod.call(other, arg);
Deprecates Object.defineProperty()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Object.defineProperty({}, 'foo', {value: 1})
Examples of correct code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Reflect.defineProperty({}, 'foo', {value: 1})
Examples of correct code for this rule with the { "exceptions": ["defineProperty"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["defineProperty"] }]*/
Object.defineProperty({}, 'foo', {value: 1})
Reflect.defineProperty({}, 'foo', {value: 1})
Deprecates Object.getOwnPropertyDescriptor()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Object.getOwnPropertyDescriptor({}, 'foo')
Examples of correct code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Reflect.getOwnPropertyDescriptor({}, 'foo')
Examples of correct code for this rule with the { "exceptions": ["getOwnPropertyDescriptor"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["getOwnPropertyDescriptor"] }]*/
Object.getOwnPropertyDescriptor({}, 'foo')
Reflect.getOwnPropertyDescriptor({}, 'foo')
Deprecates Object.getPrototypeOf()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Object.getPrototypeOf({}, 'foo')
Examples of correct code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Reflect.getPrototypeOf({}, 'foo')
Examples of correct code for this rule with the { "exceptions": ["getPrototypeOf"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["getPrototypeOf"] }]*/
Object.getPrototypeOf({}, 'foo')
Reflect.getPrototypeOf({}, 'foo')
Deprecates Object.setPrototypeOf()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Object.setPrototypeOf({}, Object.prototype)
Examples of correct code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Reflect.setPrototypeOf({}, Object.prototype)
Examples of correct code for this rule with the { "exceptions": ["setPrototypeOf"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["setPrototypeOf"] }]*/
Object.setPrototypeOf({}, Object.prototype)
Reflect.setPrototypeOf({}, Object.prototype)
Deprecates Object.isExtensible
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Object.isExtensible({})
Examples of correct code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Reflect.isExtensible({})
Examples of correct code for this rule with the { "exceptions": ["isExtensible"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["isExtensible"] }]*/
Object.isExtensible({})
Reflect.isExtensible({})
Deprecates Object.getOwnPropertyNames()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Object.getOwnPropertyNames({})
Examples of correct code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Reflect.getOwnPropertyNames({})
Examples of correct code for this rule with the { "exceptions": ["getOwnPropertyNames"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["getOwnPropertyNames"] }]*/
Object.getOwnPropertyNames({})
Reflect.getOwnPropertyNames({})
Deprecates Object.preventExtensions()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Object.preventExtensions({})
Examples of correct code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
Reflect.preventExtensions({})
Examples of correct code for this rule with the { "exceptions": ["preventExtensions"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["preventExtensions"] }]*/
Object.preventExtensions({})
Reflect.preventExtensions({})
Deprecates the delete keyword
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
delete foo.bar; // deleting object property
Examples of correct code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
delete bar; // deleting variable
Reflect.deleteProperty(foo, 'bar');
Note: For a rule preventing deletion of variables, see no-delete-var instead
Examples of correct code for this rule with the { "exceptions": ["delete"] } option:
/*eslint prefer-reflect: ["error", { "exceptions": ["delete"] }]*/
delete bar
delete foo.bar
Reflect.deleteProperty(foo, 'bar');
This rule should not be used in ES3/5 environments.
In ES2015 (ES6) or later, if you don't want to be notified about places where Reflect could be used, you can safely disable this rule.
This rule was introduced in ESLint 1.0.0-rc-2.
© JS Foundation and other contributors
Licensed under the MIT License.
https://eslint.org/docs/rules/prefer-reflect