Get a specific value from a JSON object through a string

Question

I'm trying to access to the hello value through a string (key) I got undefined. I'm out of idea to make it works.

var key = "a.b.c.0";
var test = {"a":{"b":{"c":["hello","world"]}}};
console.log(test[key]); // undefined

console.log(test["a.b.c.0"]); // undefined
console.log(test["a.b.c[0]"]); // undefined
console.log(test["a.b.c"]); // fail
console.log(test.a.b.c); // [ 'hello', 'world' ]
console.log(test.a.b.c[0]); // hello

tooting my own horn but https://github.com/r3mus/objectkit – brandonscript Nov 28 '15 at 20:31 — brandonscript, Nov 28 '15 at 20:31

score 3 · Answer 1 · answered Nov 28 '15 at 20:26

You can do something like this, but not sure how far it'll get you:

key.split('.').reduce(function(test, prop) {
  return test[prop];
}, test);

Examples

'a.b.c.0'.split('.').reduce(function(test, prop) {...
// => "hello"

'a.b.c'.split('.').reduce(function(test, prop) {...
// => ["hello", "world"]

score 0 · Accepted Answer · edited May 23 '17 at 12:15

If you willing to use a library I highly recommend checking out lodash. For this you can use lodash's get method https://lodash.com/docs#get

_.get(test, key);

Or if you need a basic native JS implementation from Access object child properties using a dot notation string

function getDescendantProp(obj, desc) {
    var arr = desc.split(".");
    while(arr.length && (obj = obj[arr.shift()]));
    return obj;
}

console.log(getDescendantProp(test, key));
//-> hello

another possible way ( I don't recommend it but it should work) is to use eval()

var value = eval('test' + key)

Get a specific value from a JSON object through a string

2 Answers2