How do I find unique values in a list of javascript objects over multiple keys?

Question

I have an array of javascript objects. Here is an example:

[{'first': 'Mary', 'last':'Smith', 'task':'managing'},
{'first': 'Mary', 'last':'Smith', 'task':'research'},
{'first': 'Henry', 'last':'Ford', 'task':'assembling'},
{'first':'Henry', 'last':'Winkler', 'task':'acting;}]

and I want to find all elements in the array that are distinct in first AND last name. The output I'm looking for is of the form:

[{'first': 'Mary', 'last':'Smith'},
 {'first': 'Henry', 'last':'Ford'},
 {'first': 'Henry', 'last':'Winkler'}]

How do I do this in javascript?

Nice problem, have you tried anything so far or have thought any ideas on how to attack it? — Javier Conde
– Javier Conde, Commented Jan 21, 2016 at 18:35
Thanks. After a while of searching around, reading documentation (lodash, underscore, plain JS, etc) to no avail, I tried looping through the initial array, checking to see if objects with the first and last values already exist in the new array, and if not pushing the new elements to the new array, but I'm not sure how to see if an object with multiple keys already exists in an array. — mgig
– mgig, Commented Jan 21, 2016 at 18:41

MinusFour · Accepted Answer · 2016-01-21 18:38:35Z

2

I would use a Map for this:

var m = new Map();
arr.forEach(function(obj){
    var name = obj.first + ' ' + obj.last;
    if(!m.has(name)){
       m.set(name, { first : obj.first, last : obj.last});
    }
});
var uniques = Array.from(m.values());

answered Jan 21, 2016 at 18:38

MinusFour

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1 Comment

mgig Over a year ago

Clever! I didn't think of turning all the values for the keys of interest into one large string to search over. This worked!

Simon H · Accepted Answer · 2016-01-21 18:43:01Z

1

This would be a good time to roll out the new ES6 set

var s = new Set();
arr.forEach(a => s.add({'first':a.first, 'last': a.last}))
var myArr = Array.from(s);

answered Jan 21, 2016 at 18:43

Simon H

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Comments

Sashi · Accepted Answer · 2016-01-21 18:48:01Z

0

@Minusfour You are just ahead of me. I got same solution.

array.forEach( function (arrayItem)
{
   if(hashMap[arrayItem.first + arrayItem.last] == 0){
     hashMap[arrayItem.first + arrayItem.last] = 1;
     finalArray.push(arrayItem);
   }
});

answered Jan 21, 2016 at 18:48

Sashi

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