prefer-reflect
Require Reflect methods where applicable
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.
Please note: This rule contains an incorrect behavior - it will suggest you to use Reflect.getOwnPropertyNames rather than Object.getOwnPropertyNames, but the former one doesn’t exist in the specification. We suggest using the exceptions option with "getOwnPropertyNames" to avoid this false suggestion.
The ES6 Reflect API comes with a handful of methods which somewhat deprecate methods on old constructors:
Reflect.applyeffectively deprecatesFunction.prototype.applyandFunction.prototype.callReflect.deletePropertyeffectively deprecates thedeletekeywordReflect.getOwnPropertyDescriptoreffectively deprecatesObject.getOwnPropertyDescriptorReflect.getPrototypeOfeffectively deprecatesObject.getPrototypeOfReflect.setPrototypeOfeffectively deprecatesObject.setPrototypeOfReflect.preventExtensionseffectively deprecatesObject.preventExtensions
The prefer-reflect rule will flag usage of any older method, suggesting to instead use the newer Reflect version.
Rule Details
Options
Exceptions
"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"] }]
Reflect.apply
Deprecates Function.prototype.apply() and Function.prototype.call()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
;
;
;
;
;
;
;
;
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);
Reflect.defineProperty
Deprecates Object.defineProperty()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
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})
Reflect.getOwnPropertyDescriptor
Deprecates Object.getOwnPropertyDescriptor()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
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')
Reflect.getPrototypeOf
Deprecates Object.getPrototypeOf()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
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')
Reflect.setPrototypeOf
Deprecates Object.setPrototypeOf()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
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)
Reflect.isExtensible
Deprecates Object.isExtensible
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
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({})
Reflect.preventExtensions
Deprecates Object.preventExtensions()
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
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({})
Reflect.deleteProperty
Deprecates the delete keyword
Examples of incorrect code for this rule when used without exceptions:
/*eslint prefer-reflect: "error"*/
; // 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');
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 places where Reflect could be used, you can safely disable this rule.
Related Rules
Version
This rule was introduced in ESLint v1.0.0-rc-2.