Getting an Objects nested value from an array of nested properties

Question

I have a situation where I need to zip two Objects together retaining both of the values. I can iterate through both the objects and build an array of all the keys.

Answer 1

Perhaps something like this?

function getValueAt(obj, keyPathArray) {
    var emptyObj = {};

    return keyPathArray.reduce(function (o, key) {
        return (o || emptyObj)[key];
    }, obj);
}

Then you can use it like:

var o = { a: { c: { d: 1 } } };

getValueAt(o, ['a', 'c', 'd']); //1

However it's not efficient for non-existing properties, since it will not short-circuit. Here's another approach without using reduce:

function getValueAt(o, keyPathArray) {
    var i = 0, 
        len = keyPathArray.length;

    while (o != null && i < len) o = o[keyPathArray[i++]];

    return o;    
}