Traverse nested structures of JavaScript objects and arrays using string paths

Question

I have a data structure like this:

var someObject = {
    'part1' : {
        'name': 'Part 1',
        'size': '20',
        'qty' : '50'
    },
    'part2' : {
        'name': 'Part 2',
        'size': '15',
        'qty' : '60'
    },
    'part3' : [
        {
            'name': 'Part 3A',
            'size': '10',
            'qty' : '20'
        }, {
            'name': 'Part 3B',
            'size': '5',
            'qty' : '20'
        }, {
            'name': 'Part 3C',
            'size': '7.5',
            'qty' : '20'
        }
    ]
};

I want to access the data using the following variables:

var part1name = "part1.name";
var part2quantity = "part2.qty";
var part3name1 = "part3[0].name";

part1name should be filled with the value of someObject.part1.name, which is "Part 1". The same goes for part2quantity, which is padded to 60.

Is there a way to achieve this using pure JavaScript or JQuery?

Answer 1

This is now supported via lodash using _.get(obj, property). See https://lodash.com/docs#get

Example from documentation:

var object = { 'a': [{ 'b': { 'c': 3 } }] };

_.get(object, 'a[0].b.c');
// → 3

_.get(object, ['a', '0', 'b', 'c']);
// → 3

_.get(object, 'a.b.c', 'default');
// → 'default'

Answer 2

I just created this based on some similar code I already had and it seems to work:

Object.byString = function(o, s) {
    s = s.replace(/\[(\w+)\]/g, '.'); // 将索引转换为属性
    s = s.replace(/^\./, '');           // 去掉前导点
    var a = s.split('.');
    for (var i = 0, n = a.length; i < n; ++i) {
        var k = a[i];
        if (k in o) {
            o = o[k];
        } else {
            return;
        }
    }
    return o;
}

usage:

Object.byString(someObj, 'part3[0].name');

View a working example at http://jsfiddle.net/alnitak/hEsys/.

EDIT Some people have noticed that this code will throw an error if passed a string where the leftmost index does not correspond to a properly nested entry in the object. This is a valid concern, but I think it's better handled using a try/catch block when called, rather than having this function silently return undefined.