Create array of values from a nested object using _Underscore

Question

I've been having a heck of a time trying to figure this out. Still relatively new to _Underscore JS and I'm attempting to create an array of unique values from an array of nested objects. Example data below:

[  
   {  
      "property":"prop1",
      "list":[  
         {  
            "description":"description blah",
            "type":"F",
            "values":{  
               "value1":30.0,
               "value2":0.0
            }
         },
         {  
            "description":"description blah",
            "type":"F",
            "values":{  
               "value1":30.0,
               "value2":0.0
            }
         }
      ]
   },
   {  
      "property":"prop2",
      "list":[  
         {  
            "description":"description blah",
            "type":"Q",
            "values":{  
               "value1":30.0,
               "value2":0.0
            }
         }
      ]
   }
]

What I'm attempting to get back is an array of ALL the UNIQUE nested "type" values. Example of data back below:

["F","Q"]

I've attempted _.pluck and _.map with little success. Would I need to utilize something different, such as chaining them? Appreciate any help I could get on this.

Gruff Bunny · Accepted Answer · 2017-06-22 08:14:47Z

2

Here's a solution that uses chaining:

let result = _.chain(data)
    .pluck('list')
    .flatten()
    .pluck('type')
    .uniq()
    .value();

This works by first plucking the lists from the data and flattening them. Then the type is plcuked from the list before finally calling uniq to get the unique types.

answered Jun 22, 2017 at 8:14

Gruff Bunny

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2 Comments

dlimes Over a year ago

Thank you! This is perfect!

Benjamints Over a year ago

Awesome answer!

tymeJV · Accepted Answer · 2017-06-21 19:02:03Z

0

You can do this regular JS and reduce (sorry, I'm not very familiar with underscore, so I figured I'd offer a vanilla solution for now)

var uniqueValues = data.reduce(function(vals, d) {
    return vals.concat(d.list.reduce(function(listVals, l) {
        if (vals.indexOf(l.type) === -1 && listVals.indexOf(l.type) === -1) {
            listVals.push(l.type)
        }

        return listVals;
    }, []))
}, [])

Demo: https://jsfiddle.net/0dsdm7Lu/

answered Jun 21, 2017 at 19:02

tymeJV

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Comments

adrice727 · Accepted Answer · 2017-06-21 19:09:00Z

0

_.unique(_.flatten(_.map(myList, item => _.map(item.list, i => i.type))));

Underscore is not the greatest when it comes to composing functions since it takes data first. lodash-fp and ramda are much better in this regard.

Working fiddle: https://jsfiddle.net/8eLk7t15/

answered Jun 21, 2017 at 19:09

adrice727

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3 Comments

dlimes Over a year ago

Unfortunately, this isn't my choice. If it were my choice, I would've chose lodash (ultimately because I've heard it tends to be superior in many ways). So I currently do have to stick with underscore. I like the clean look to lodash though, thanks anyways :(

adrice727 Over a year ago

It's actually underscore.

dlimes Over a year ago

I apologize, I thought you were suggesting lodash, and supplying lodash code. Should've looked closer at your jsfiddle. Although I do still prefer the chaining method utilized by accepted answer. Thanks bud!

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