Question

How can I reach into a object using an array and set a value – preferably without using eval, doing something like object[eval(["key", "deepkey"].split("")) = "newvalue"?

Doing it manually, I would just do object.key.deepkey = "newvalue", but again, I need to do this using an array to reach into the right property.

The object for reference:

object = {
  key: {
    deepKey: "value"
  }
}

Answer 1

You can use a recursive function to step through each level of the array (or object) like so:

function val(array, indices) {
    if(indices.length > 1) {
        var idx = indices.shift();
        return val(array[idx], indices);
    }
    else {
        return array[indices.shift()];
    }
}

var obj = { a: { b: 'c' } };

//result is 'c'
var result = val(obj, ['a', 'b']);

If you want to get an object reference, simply specify the second arg only up to that:

var obj = {
    a: {
        b: {
            c: 'foo'
        }
    }
};

var ref = val(obj, ['a', 'b']);

//ref is now obj.a.b, so you can do something like...
ref.x = 'bar';

console.dir(ref); //outputs something like { c: 'foo', x: 'bar' }