How to access key values in an object using d3.js?

Question

I have an array named "dataset" where each entry is an object with a key and value attribute, such as the following:

dataset= 
 [
 {"key":"alpha", "value": [ {}, { } ...]},
 {"key":"beta", "value": [ { }, { } ...]},
 {"key":"gamma", "value": [ {}, { } ...]},
 {"key":"delta", "value": [ { }, { } ...]}
 ];
 dataset.domain:[];
 dataset.query:[];
 dataset.range:[];

I am working with D3.JS and I am using this dataset to plot in an stacked area chart the alpha, beta, gamma, and delta values. How can I use color.domain() to assign a different color to each "key"?

You cannot have the same key twice in an object. Is this really how your structure looks? Not some all these key/value pairs wrapped in an array? — Thilo
– Thilo, Commented Apr 3, 2014 at 21:50
@Thilo: I'm assuming that each key/value row should be wrapped in {}..., so the total structure is an array of objects, each of which contains a key name and a value sub-array. — AmeliaBR
– AmeliaBR, Commented Apr 3, 2014 at 22:00

AmeliaBR · Accepted Answer · 2014-04-03 22:02:22Z

2

To create an array that contains one property from each object in your data array, use an array mapping function:

dataset=  [
 {"key":"alpha", "value": [ {}, { } ...]},
 {"key":"beta", "value": [ { }, { } ...]},
 {"key":"gamma", "value": [ {}, { } ...]},
 {"key":"delta", "value": [ { }, { } ...]}
 ];

domain = dataset.map(function(o){return o.key});
/* domain is now ["alpha", "beta", "gamma", "delta"] */

answered Apr 3, 2014 at 22:02

AmeliaBR

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