How to convert an array into an object?

What is the best way to convert:

['a','b','c']

to:

{
  0: 'a',
  1: 'b',
  2: 'c'
}

ECMAScript 6 introduces the easily polyfillable Object.assign:

The Object.assign() method is used to copy the values of all
enumerable own properties from one or more source objects to a target
object. It will return the target object.

Object.assign({}, ['a','b','c']); // {0:"a", 1:"b", 2:"c"}

The own length property of the array is not copied because it isn't enumerable.

Also, you can use ES8 spread syntax on objects to achieve the same result:

{ ...['a', 'b', 'c'] }

For custom keys you can use reduce:

['a', 'b', 'c'].reduce((a, v) => ({ ...a, [v]: v}), {}) 
// { a: "a", b: "b", c: "c" }

Stack Overflow Q#4215737, score: 1061