Finding my object inside JSON by its ID

Question

[
    {"ID":"5","Name":"Jay"},
    {"ID":"30","Name":"Sharon"},
    {"ID":"32","Name":"Paul"}
]

So I have this kind of JSON.

I need to easily supply the value for a required key. For example:

30 would yield => "Sharon"
5 would yield => "Jay"

etc. What is the right way to do this?

If they're not sorted, there's no other way but to do a linear search. — GJK, Jun 26 '13 at 00:06
Look at every object until you find the one you're looking for,. — , Jun 26 '13 at 00:07
Refer to this post: http://stackoverflow.com/questions/1946165/json-find-in-javascript — Guilherme Lopes, Jun 26 '13 at 00:13

adeneo · Answer 1 · 2013-06-26T00:26:05.733

5

Iterate the array and check if the ID matches

function getById(id) {
    var O = null;
    for (var i=0; i<arr.length; i++) {
        if ( arr[i].ID == id ) return O = arr[i];
    }
    return O;
}

getById('30'); // returns {"ID":"30","Name":"Sharon"}

FIDDLE

or in newer browsers:

function getById(arr, id) {
   return arr.filter(function(o) { return o.ID == id });
}

FIDDLE

edited Jun 26 '13 at 00:26

answered Jun 26 '13 at 00:10

adeneo

303,455
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2

You could return from within the if statement to avoid checking the rest of the array – bfavaretto Jun 26 '13 at 00:18
1

@bfavaretto - seems like a good idea, and just returning the assigment should do that. – adeneo Jun 26 '13 at 00:24

score 3 · Answer 2 · edited Jun 26 '13 at 00:14

3

Try a linear search:

var searchId = "30";
for(var i = 0; i < json.length; i++)
{
    if(json[i].ID == searchId)
    {
        // Found it.
        //

        break;
    }
}

edited Jun 26 '13 at 00:14

Marty

38,275
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answered Jun 26 '13 at 00:08

bugwheels94

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score 2 · Answer 3 · answered Jun 26 '13 at 00:11

If the IDs will be unique, and if you're going to need to do this frequently, then you may want to convert your collection to key/value pairs where the ID is the key.

var byId = data.reduce(function(res, obj) {
    res[obj.ID] = obj;
    return res
}, {});

Now you can simply use the ID to look up the object.

var target = byId["30"];

score 1 · Answer 4 · answered Jun 26 '13 at 00:14

1

You could probably just write something to loop through it.

var data = [ {"ID":"5","Name":"Jay"},{"ID":"30","Name":"Sharon"}, {"ID":"32","Name":"Paul"} ];
for(var i in data){
    if(data[i]["ID"] == 30){
      return data[i]["Name"];
    }
}

answered Jun 26 '13 at 00:14

Neuticle

614
3
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Ikhoon Eom · Answer 5 · 2013-06-26T04:10:39.237

0

undersocre.js can find a object in collection by one line code

Reference: http://underscorejs.org/#find

Code:

var people = [
    {"ID":"5","Name":"Jay"},
    {"ID":"30","Name":"Sharon"},
    {"ID":"32","Name":"Paul"}
];

_.find(people, function(person) { return person.ID === '5'; });

FIDDLE

edited Jun 26 '13 at 04:10

answered Jun 26 '13 at 00:51

Ikhoon Eom

183
2
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Finding my object inside JSON by its ID

5 Answers5