Reference nested json object property by string

Question

I know I'm missing something obvious here but say I have a JSON object that looks like this:

testObj = {
            levelOne: {
                       levelTwo: []
            }
}

I also have a string value:

var prop = 'levelOne.levelTwo';

I'm trying to determine if there's any way to basically do something like this:

var x = testObj[prop];

That doesn't work, but is there any way to do the equivalent?

score 5 · Accepted Answer · answered Jun 17 '19 at 20:49

5

There's no trivial way (e.g. testObj[prop]) of doing this, but the reduce function is well suited:

let nestedProp = (obj, path) =>
 path.split('.').reduce((obj, prop) => obj[prop], obj);

let x = nestedProp({levelOne: {levelTwo: [5]}}, 'levelOne.levelTwo');
console.log(x);

answered Jun 17 '19 at 20:49

junvar

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Brilliant, thanks - I knew there had to be a simple way to do this. This gives me exactly what I was looking for. – monkeyWithAMachinegun Jun 17 '19 at 21:01

score 0 · Answer 2 · answered Jun 17 '19 at 20:49

You can use dynamic keys to access properties in an object but not multiple levels down.

i.e. You can do const a = testObject["levelOne"] but not what you tried. (Docs)

There are however helper libs that have functions to do this. One example is lodash.get function

Reference nested json object property by string

2 Answers2