Underscore.js Find and return element in nested array

Question

I have data-structure like this:

[
    {
        "name": "AAAA",
        "children": [
            {"name": "vvv", "id": 3},
            {"name": "vvv22", "id": 4}
        ]
    },
    {
        "name": "BBBB",
        "children": [
            {"name": "ggg", "id": 5},
            {"name": "ggggv22", "id": 6}
        ]
    },
]

And I want to find and return child with given ID. How to achieve this using Underscore.js?

My current realisation without using Underscore:

for (var i = 0; i < data.length; i++) {
     var dataItem= data[i];
     for (var j = 0; j < dataItem.children.length; j++) {
        var child = dataItem.children[j];
        if (child .id == id) {
             return child;  
        }
     }
}

nikoshr · Accepted Answer · 2020-10-21 12:45:15Z

21

Pluck the children keys from your top level objects
Flatten the resulting array
Find the first object matching the condition, e.g having the correct id
Chain these operations

which leads to

var res = _(data).chain().
    pluck('children').
    flatten().
    findWhere({id: 3}).
    value();

And a demo

var data = [
    {
        "name": "AAAA",
        "children": [
            {"name": "vvv", "id": 3},
            {"name": "vvv22", "id": 4}
        ]
    },
    {
        "name": "BBBB",
        "children": [
            {"name": "ggg", "id": 5},
            {"name": "ggggv22", "id": 6}
        ]
    }
];
var res = _(data).chain().
    pluck('children').
    flatten().
    findWhere({id: 3}).
    value();
    
console.log(res);

<script src="http://underscorejs.org/underscore-min.js"></script>

edited Oct 21, 2020 at 12:45

answered Jul 15, 2014 at 11:29

nikoshr

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3 Comments

Bob Over a year ago

Am I right that this example will only go 2 levels deep? I am looking for an example that can handle variable levels deep...

nikoshr Over a year ago

That's right. For a variable depth, you probably would use a recursion. Feel free to ask a question if you can't find what you want

user2576960 Over a year ago

I'm trying to use this by matching against an outside variable in the findWhere statement but it would appear the variable is not available to the methods. How would I handle this? Thanks.

Mritunjay · Accepted Answer · 2014-07-15 11:40:02Z

4

I got this function using underscore which will do your work.

var getChild = function(id,data){
    var allChildren = _.flatten(_.pluck(data,'children'));
    var childWithId = _.find(allChildren,function(child){return child.id == id});
    return childWithId;
}

var child = getChild(5,data);
console.log(child);

edited Jul 15, 2014 at 11:40

answered Jul 15, 2014 at 11:29

Mritunjay

25.9k7 gold badges57 silver badges71 bronze badges

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