In Javascript a dictionary comprehension, or an Object `map`

Question

I need to generate a couple of objects from lists in Javascript. In Python, I\'d write this:

{key_maker(x): val_maker(x) for x in a_list}

A

Answer 1

ES5 introduced Map for an OrderedDict. A Map comprehension might look like:

Map( Array.map(function(o){return[ key_maker(o), val_maker(o) ]}))

Example:

> a_list = [ {x:1}, {x:2}, {x:3} ]
< [ Object, Object, Object ]
>
> let dict = new Map(a_list.map(function(o){return[ o.x, o.x**2 ]}))
< Map[3]
< 0 : {1 => 1}
< 1 : {2 => 4}
< 2 : {3 => 9}
>
> dict.get(2)
< 4