Array.prototype[Symbol.unscopables]

The @@unscopables data property of Array.prototype is shared by all Array instances. It contains property names that were not included in the ECMAScript standard prior to the ES2015 version and that are ignored for with statement-binding purposes.

Value

A null-prototype object with property names given below and their values set to true.

Description

The default Array properties that are ignored for with statement-binding purposes are:

• at()
• copyWithin()
• entries()
• fill()
• find()
• findIndex()
• flat()
• flatMap()
• includes()
• keys()
• values()

Array.prototype[@@unscopables] is an empty object only containing all the above property names with the value true. Its prototype is null, so Object.prototype properties like toString won't accidentally be made unscopable, and a toString() within the with statement will continue to be called on the array.

See Symbol.unscopables for how to set unscopable properties for your own objects.