Getting a value from a JSON object by its path

Question

I'm getting a big, nested JSON response from an online API. I require only 3 values from it, but they are quite nested. I do know the exact path to each of those fields. For example, given:

obj = {
    "result": {
        "data": {
            "point1": "x",
            "value": 2
        },
        "foo": {
            "bar": 7
        }
    }
}

And the path let p = 'result.data.value' I'd like to be able to do let x = getElement(obj, p); and have x be 2.

I wrote a simple function (removed all the error checking to keep clean):

const getJSONElement = (data, path) => {
  for(let p of path.split('.')) {
    data = data[p];
  }
  return data;
};

It works, but I feel like I'm missing something, or not being efficient. Is there there's a better way to get to the element (perhaps using Array.reduce)?

If importing a library is an option, i'd recommend selectn: https://github.com/wilmoore/selectn.js . It will work for your case, but can also handle null checks, array indices, etc. — Nicholas Tower, Sep 13 '17 at 18:23
Or https://stackoverflow.com/questions/8817394/javascript-get-deep-value-from-object-by-passing-path-to-it-as-string or https://stackoverflow.com/questions/6491463/accessing-nested-javascript-objects-with-string-key or https://stackoverflow.com/questions/8051975/access-object-child-properties-using-a-dot-notation-string or https://stackoverflow.com/questions/6393943/convert-javascript-string-in-dot-notation-into-an-object-reference — user229044, Sep 13 '17 at 18:28
Thanks @meagar, I tried searching for similar questions, but I guess I didn't try well enough. At any rate, I got the answer using `reduce` so that's a plus :) — Traveling Tech Guy, Sep 13 '17 at 18:37

score 3 · Accepted Answer · answered Sep 13 '17 at 18:25

You could reduce the object with the splitted path values.

var object = { result: { data: { point1: "x", value: 2 }, foo: { bar: 7 } } },
    path = 'result.data.value',
    getValue = (o, p) => p.split('.').reduce((r, k) => r[k], o);

console.log(getValue(object, path));

Getting a value from a JSON object by its path

1 Answers1