Stage 3 Draft / October 16, 2018

Object.fromEntries

Introduction

Object.fromEntries takes a list of key-value pairs, such as that produced by Object.entries, and returns a new object whose properties are given by those entries. Its argument iterable is expected to be an object that implements an @@iterator method, that returns an iterator object, that produces a two element array-like object, whose first element is a value that will be used as a property key, and whose second element is the value to associate with that property key.

1Object.fromEntries ( iterable )

When the fromEntries method is called with argument iterable, the following steps are taken:

  1. Perform ? RequireObjectCoercible(iterable).
  2. Let obj be ObjectCreate(%ObjectPrototype%).
  3. Assert: obj is an extensible ordinary object with no own properties.
  4. Let stepsDefine be the algorithm steps defined in CreateDataPropertyOnObject Functions.
  5. Let adder be CreateBuiltinFunction(stepsDefine, « »).
  6. Return ? AddEntriesFromIterable(obj, iterable, adder).
Note
The function created for adder is never directly accessible to ECMAScript code.

2CreateDataPropertyOnObject Functions

A CreateDataPropertyOnObject function is an anonymous built-in function. When a CreateDataPropertyOnObject function is called with arguments key and value, the following steps are taken:

  1. Let O be the this value.
  2. Assert: Type(O) is Object.
  3. Assert: O is an extensible ordinary object.
  4. Let propertyKey be ? ToPropertyKey(key).
  5. Perform ! CreateDataPropertyOrThrow(O, propertyKey, value).

ACopyright & Software License

Copyright Notice

© 2018 Darien Maillet Valentine, Jordan Harband, Kevin Gibbons

Software License

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