Querying an array of objects

Question

Anyone have guidance on how to query an array of hashes in coffeescript?

For example, I have an array of hashes, each with a "name" and "setting":

[
  {"name":"color", "setting":"red"},
  {"name":"scale_min", "setting":"15"},
  {"name":"scale_type", "setting":"linear"},
  {"name":"x_axis_label", "setting":"Weeks"}
]

I want to find the element in this array where the hash "name" is "x_axis_label"

How can I easily do that with coffeescript?

I need some kind of value_for_key_in_object(key, object) function and figured if would be part of the lexicon...

gen_Eric · Accepted Answer · 2012-05-30 16:14:20Z

33

I just hacked this up quickly:

data = [{"name":"color","setting":"red"},{"name":"scale_min","setting":"15"},{"name":"scale_type","setting":"linear"},{"name":"x_axis_label","setting":"Weeks"}]

find = (i for i in data when i.name is 'x_axis_label')[0]

alert(find.setting)

Demo

answered May 30, 2012 at 16:14

gen_Eric

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1 Comment

Dave Sag Over a year ago

That is awesome, and why I am really starting to love Coffeescript

Larry Maccherone · Accepted Answer · 2012-05-30 18:11:20Z

12

If you going to do this repeatedly, always looking for things where the name equals something, then you are better off converting this from an array of maps to just a map where the key is the name.

data = [
  {"name":"color","setting":"red"}
  {"name":"scale_min","setting":"15"}
  {"name":"scale_type","setting":"linear"}
  {"name":"x_axis_label","setting":"Weeks"}
]

myMap = {}
for row in data
  myMap[row.name] = row.setting

alert(myMap['x_axis_label'])

Demo

answered May 30, 2012 at 18:11

Larry Maccherone

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Comments

AA. · Accepted Answer · 2014-06-03 09:07:52Z

10

I always prefer a 'multi language' solution over a 'idiomatic' solution. Thus you can to use Array.filter

data = [{"name":"color","setting":"red"},{"name":"scale_min","setting":"15"},{"name":"scale_type","setting":"linear"},{"name":"x_axis_label","setting":"Weeks"}]
find = (data.filter (i) -> i.name is 'x_axis_label')[0]
alert find.setting

answered Jun 3, 2014 at 9:07

AA.

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Comments

epidemian · Accepted Answer · 2012-05-30 16:42:04Z

8

If you happen to be using Underscore.js, you can use find:

xAxisLabel = _.find data, (datum) -> datum.name is 'x_axis_label'

answered May 30, 2012 at 16:42

epidemian

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