How to get child object's element?

Question

How to get e's value without knowing which group, which means only use obj and e?

And also can use same way to get a.

Thanks

let obj:Object = {
  a: 'value1',
  b: 'value2',
  group1: {
    c: 'value3',
    d: 'value4'
  },
  group2: {
    e: 'value5',
    f: 'value6'
  }
};

Besides flattening out the object, there really is no way to accomplish what you're asking for. — ndugger, Feb 22 '16 at 17:52

dave · Accepted Answer · 2016-02-22T18:32:31.417

4

I would do it like this:

function findValue(key, obj) {
    for (var i in obj) {
        if (obj.hasOwnProperty(i)) {
            if (i === key) {
                return obj[i];
            } else if (typeof(obj[i]) == "object") {
                var value = findValue(key, obj[i]);
                if (typeof(value) !== "undefined") { return value; }
            }
        }
    }
}

findValue('a', obj);
//"value1"
findValue('e', obj);
//"value5"

edited Feb 22 '16 at 18:32

answered Feb 22 '16 at 17:58

dave

62,300
5
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Nice use of recursion there. – Rohit416 Feb 22 '16 at 18:01
amazing!! it works even in group's group's group, etc. thank you so much! – Hongbo Miao Feb 22 '16 at 18:04
you may have a problem with falsey values. – Nina Scholz Feb 22 '16 at 18:07
1

@NinaScholz good call, fixed – dave Feb 22 '16 at 18:32

madox2 · Answer 2 · 2016-02-22T17:57:36.787

2

You can use Object.keys() to iterate through properties and Object.hasOwnProperty() to test if object contains property:

let key = Object.keys(obj)
                .find(k => obj[k].hasOwnProperty('e'));

console.log(obj[key].e);

edited Feb 22 '16 at 17:57

answered Feb 22 '16 at 17:55

madox2

49,493
17
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thanks! is there a universal way? because now I cannot find `a`, `console.log(obj[key].a);` – Hongbo Miao Feb 22 '16 at 17:57
This isn't flexible for other levels of nesting. – lintmouse Feb 22 '16 at 18:00
@HongboMiao this works only for 1 nested level as you originally asked. dave's answer works good also for nested objects – madox2 Feb 22 '16 at 18:08
@madox2 yeah, I got it, still thanks!! – Hongbo Miao Feb 22 '16 at 18:10

Nina Scholz · Answer 3 · 2017-04-03T12:55:15.810

Version which returns falsy values, too.

function find(key, object) {
    var value;
    Object.keys(object).some(function (k) {
        if (key === k) {
            value = object[k];
            return true;
        }
        if (typeof object[k] === 'object') {
            value = find(key, object[k]);
            return value !== undefined;
        }
    });
    return value;
}

var obj = { a: 'value1', b: 'value2', group1: { c: 'value3', d: 'value4' }, group2: { e: 'value5', f: 'value6' }, group3: { g: '', h: 0 } };

document.write(find('e', obj) + '<br>');
document.write(find('g', obj) + '<br>');
document.write(find('h', obj) + '<br>');

How to get child object's element?

3 Answers3

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