Using Array objects as key for ES6 Map

Question

I am trying to update my code to ES6 as I am using Node 4.0 and really like its features so far. However I have problems with the new ES6 Map data structure as

Answer 1

I also had this need, so I wrote an ISC-licensed library: array-keyed-map. You can find it on npm. I think the source is quite clear, but here's how it works anyway, for posterity:

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Maintain a tree of Map objects. Each tree stores:

• Under an internally-declared Symbol key: The value at that point in the tree (if any). The Symbol guarantees uniqueness, so no user-provided value can overwrite this key.

• On all its other keys: all other so-far set next-trees from this tree.

For example, on akmap.set(['a', 'b'], true), the internal tree structure would be like—

'a':
  [value]: undefined
  'b':
    [value]: true

Doing akmap.set(['a'], 'okay') after that would just change the value for the path at 'a':

'a':
  [value]: 'okay'
  'b':
    [value]: true

To get the value for an array, iterate through the array while reading the corresponding keys off the tree. Return undefined if the tree at any point is non-existent. Finally, read the internally declared [value] symbol off the tree you've gotten to.

To delete a value for an array, do the same but delete any values under the [value]-symbol-key, and delete any child trees after the recursive step if they ended up with a size of 0.

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Why a tree? Because it's very efficient when multiple arrays have the same prefixes, which is pretty typical in real-world use, for working with e.g. file paths.