How extract object by key/value from array using an other array

Question

assuming we have two arrays like that :

var array1 = [
    {"name":"foo", "age": 13},
    {"name":"bar", "age": 15},
    {"name":"foobar", "age": 9},

    {"name":"i", "age": 60},
    {"name":"want", "age": 41},
    {"name":"to", "age": 31},
    {"name":"extract", "age": 2},
    {"name":"all", "age": 34},
    {"name":"these", "age": 54}
];

var array2 = [
    {"name":"foo", "age": 13},
    {"name":"bar", "age": 15},
    {"name":"foobar", "age": 9}
];

I would like to extract from array1 all objects i have not in array2 using the key name as reference. So at the end of the treatment, I would like to have the array :

var expectedResults = [
    {"name":"i", "age": 60},
    {"name":"want", "age": 41},
    {"name":"to", "age": 31},
    {"name":"extract", "age": 2},
    {"name":"all", "age": 34},
    {"name":"these", "age": 54}
}

Any idea to do that ? I can't find a method in JS which seems to allow that kind of filter.

Just loop through the initial array, and keep the ones you need. — Kaarel Nummert
– Kaarel Nummert, Commented Jul 10, 2014 at 14:32
" I can't find a method in JS which seems to allow that kind of filter." You know... sometimes you actually need to write a little code. — cookie monster
– cookie monster, Commented Jul 10, 2014 at 14:39
@kl94: It's the simplest thing that could work. I suggest you don't try to do premature optimization, and just get it to work first. From your question I got the impression you hadn't even managed to get it to work yet. — Kaarel Nummert
– Kaarel Nummert, Commented Jul 10, 2014 at 14:39
@cookiemonster Agree, but in some others languages. You can do it easily — klefevre
– klefevre, Commented Jul 10, 2014 at 14:41

thefourtheye · Accepted Answer · 2014-07-10 14:58:24Z

4

You can get all the names from array2 like this

var names = array2.map(function(currentObject) {
    return currentObject.name;
});

And filter objects from array1, based on the gathered names like this

var result = array1.filter(function(currentObject) {
    return names.indexOf(currentObject.name) === -1;
});

console.log(result);

Output

[ { name: 'i', age: 60 },
  { name: 'want', age: 41 },
  { name: 'to', age: 31 },
  { name: 'extract', age: 2 },
  { name: 'all', age: 34 },
  { name: 'these', age: 54 } ]

As you want to make the code a little shorter, you can do something like this

var result = array1.filter(function(currentObject) {
    return array2.every(function(currentArray2Object) {
        return currentArray2Object.name !== currentObject.name;
    })
});

But if the arrays are big, then the efficient solution would be

var names = array2.reduce(function(result, currentObject) {
    result[currentObject.name] = currentObject.age;
    return result;
}, {});

var result = array1.filter(function(currentObject) {
    return !names.hasOwnProperty(currentObject.name);
});

console.log(result);

edited Jul 10, 2014 at 14:58

answered Jul 10, 2014 at 14:34

thefourtheye

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7 Comments

klefevre Over a year ago

Thanks for your answer, it did the work done. But I really thought there was a better way to do kind of work. Thanks again.

thefourtheye Over a year ago

@kl94 By better, you mean shorter or efficient?

klefevre Over a year ago

I was looking for a shorter solution, but I think we just can't. Once again, thanks you.

thefourtheye Over a year ago

@kl94 I just included an alternate version, please check.

thefourtheye Over a year ago

@BenjaminAnderson Thanks :-) I also included an efficient version, please check.

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