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Proxy.handler

The proxy's handler object is a placeholder object which contains traps for proxies.

Methods

All traps are optional. If a trap has not been defined, the default behavior is to forward the operation to the target.

handler.getPrototypeOf(): A trap for Object.getPrototypeOf.
handler.setPrototypeOf(): A trap for Object.setPrototypeOf.
handler.isExtensible(): A trap for Object.isExtensible.
handler.preventExtensions(): A trap for Object.preventExtensions.
handler.getOwnPropertyDescriptor(): A trap for Object.getOwnPropertyDescriptor.
handler.defineProperty(): A trap for Object.defineProperty.
handler.has(): A trap for the in operator.
handler.get(): A trap for getting property values.
handler.set(): A trap for setting property values.
handler.deleteProperty(): A trap for the delete operator.
handler.ownKeys(): A trap for Object.getOwnPropertyNames and Object.getOwnPropertySymbols.
handler.apply(): A trap for a function call.
handler.construct(): A trap for the new operator.

Some non-standard traps are obsolete and have been removed.

Specifications

Specification	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Proxy Object Internal Methods and Internal Slots' in that specification.	Standard	Initial definition.
ECMAScript Latest Draft (ECMA-262) The definition of 'Proxy Object Internal Methods and Internal Slots' in that specification.	Living Standard	The `enumerate` handler has been removed.

Browser compatibility

Feature	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
`apply`	49	12	18	No	36	10
`construct`	49	12	18	No	36	10
`defineProperty`	49	12	18	No	36	10
`deleteProperty`	49	12	18	No	36	10
`enumerate`	No	No	37 — 47	No	No	No
`get`	49	12	18	No	36	10
`getOwnPropertyDescriptor`	49	12	18	No	36	10
`getPrototypeOf`	No	No	49	No	No	No
`has`	49	12	18	No	36	10
`isExtensible`	?	?	31	No	?	?
`ownKeys`	49	12	18¹	No	36	10
`preventExtensions`	49	12	22	No	36	10
`set`	49	12	18	No	36	10
`setPrototypeOf`	?	?	49	No	?	?

Feature	Android webview	Chrome for Android	Edge mobile	Firefox for Android	IE mobile	Opera Android	iOS Safari
`apply`	49	49	Yes	18	No	36	10
`construct`	49	49	Yes	18	No	36	10
`defineProperty`	49	49	Yes	18	No	36	10
`deleteProperty`	49	49	Yes	18	No	36	10
`enumerate`	No	No	No	37 — 47	No	No	No
`get`	49	49	Yes	18	No	36	10
`getOwnPropertyDescriptor`	49	49	Yes	18	No	36	10
`getPrototypeOf`	No	No	No	49	No	No	No
`has`	49	49	Yes	18	No	36	10
`isExtensible`	?	?	?	31	No	?	?
`ownKeys`	49	49	Yes	18¹	No	36	10
`preventExtensions`	49	49	Yes	22	No	36	10
`set`	49	49	Yes	18	No	36	10
`setPrototypeOf`	?	?	?	49	No	?	?

1. In Firefox 42, the implementation got updated to reflect the final ES2015 specification: The result is now checked if it is an array and if the array elements are either of type string or of type symbol. Enumerating duplicate own property names is not a failure anymore.

Proxy.handler

Methods

Specifications

Browser compatibility

See also