Filter array of objects by object key

Question

I have an array of objects in Javascript:

var List = [
            {
                employee:'Joe',
                type:'holiday',
            },
            {
                employee:'Jerry',
                type:'seminar',

            },
            {
                employee:'Joe',
                type:'shore leave',
            }
           ];

I would like to obtain two new arrays of objects; one for the key employee "Joe" and the other for the key employee "Jerry". The objects should keep the same pairs of key/values.

I have been trying to get a solution using underscore.js, but it is getting too complicated. Any ideas on how this can be achieved?

Do you want to provide the names or do you want to group the object automatically by name? Please post what you have tried so far. — Felix Kling
– Felix Kling, Commented Mar 7, 2013 at 15:11
There are 2 "Joe"s. What do you want the result to look like? — gen_Eric
– gen_Eric, Commented Mar 7, 2013 at 15:19

Ben McCormick · Accepted Answer · 2013-03-07 15:31:09Z

6

var joe = List.filter(function(el){
 return el.employee === "Joe"
});

var jerry = List.filter(function(el){
 return el.employee === "Jerry"
});

This uses Array.prototype.filter and will work in IE9 and up + all recent Chrome/Firefox/Safari/Opera releases.

If you don't know the names in advance then you can create a map var names = {};

for(var i =0; i<List.length; i++){
  var ename = List[i].employee;
  if(typeof names[ename] === "undefined"){
     names[ename] = List.filter(function(el){
     return el.employee === "ename"
    });
   }

}

As a side note, Javascript convention is to only capitalize the first letter of a variable for constructors. So List should probably be list.

edited Mar 7, 2013 at 15:31

answered Mar 7, 2013 at 15:15

Ben McCormick

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Comments

Diode · Accepted Answer · 2013-03-07 15:24:25Z

4

var emps = {};  
_.each(List, function(item){
   emps[item.employee] = emps[item.employee] || [];
   emps[item.employee].push(item);
});

or using groupBy

var emps = _.groupBy(List, function(item){
   return item.employee;
});

console.log(emps); gives

{
    "Jerry": [
        {
            "employee": "Jerry",
            "type": "seminar"
        }
    ],
    "Joe": [
        {
            "employee": "Joe",
            "type": "holiday"
        },
        {
            "employee": "Joe",
            "type": "shore leave"
        }
    ]
}

edited Mar 7, 2013 at 15:24

answered Mar 7, 2013 at 15:17

Diode

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Comments

GenKali · Accepted Answer · 2014-01-28 09:39:03Z

0

Sorry - I don't have the rep. to comment yet but I believe it should be

return el.employee === ename;  // No quotes around ename

Otherwise the answer @Ben gives is perfect - it can be extended into a 'groupby' function if using underscore is out of the question a the project.

answered Jan 28, 2014 at 9:39

GenKali

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Comments

Julian Gonggrijp · Accepted Answer · 2021-02-17 17:28:53Z

0

For completeness, there is also Underscore's version of _.filter which works with the _.matcher iteratee shorthand. This is essentially a much shorter version of Ben McCormick's answer.

var joe = _.filter(List, {employee: 'Joe'});
var jerry = _.filter(List, {employee: 'Jerry'});

answered Feb 17, 2021 at 17:28

Julian Gonggrijp

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