February 2018
Intermediate to advanced
298 pages
8h 22m
English
Content preview from Learn ECMAScript - Second Edition
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Rules for using ownKeys trap
These rules shouldn't be violated when using the ownKeys trap:
- The elements of the returned array must either be a string or symbol
- The returned array must contain the keys of all the non-configurable own properties of the target object
- If the target object is not-extensible, then the returned array must contain all the keys of the own properties and of the target object, and no other values
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