_.pairs and maps

[jdalton]

I was working with maps and reached for a _.pairs method to get its key-value pairs and thought it would be handy to support.

var m = new Map([['a', 1], ['b', 2]]);
_.pairs(m);
// => [['a', 1], ['b', 2]]

[penDerGraft]

I would be up for working on this. Are you thinking this would just add a for..of loop in the existing _.pairs method, assuming it is an instanceof Map?

[jdalton]

Yep! I was thinking just for maps at the moment using _.isMap.

[penDerGraft]

Looks like there are several compatibility issues with different versions of node. in v0.10.* and below, there's an error parsing for..of. in v.0.12.*, Map is defined, but Array.from is not supported.

I think the best way to handle it is to iterate from 0 to map.size and push entries().next().value into the return array. Any other ideas?

[jdalton]

fyi I created poll to see what folks expected the behavior of maps to be.
Results are ~50/50.

[jridgewell]

Why would it be []?

[jdalton]

That's what the current draft spec has as its behavior.
It just iterates over an object's own enumerable keys.

[jridgewell]

Well, I should have read the spec. I was expecting something like the Reflect API, were it's just what Map#entries does.

[jdalton]

Ya, I think it's kinda goofy for a method called entries to not return a map's entries.

[jgonggrijp]

Special case of #2147.