Recursive string parsing into object

Question

Hello guys I'm trying to parse an array of strings into a custom structure:

var str = [
"country.UK.level.1",
"country.UK.level.2",
"country.US.level.1",
"country.UK.level.3"
];

Into something like:

var ordered = {
   "country": [
      {"UK" : {"level" : ["1", "2", "3"]}},
      {"US" : {"level" : ["1","2"]}}
   ]
}

Notes:

Strings stored in the str array will not be sorted and the code should be robust against that.
Strings will follow the x.y.x.y... pattern, where x will be unique for that array and y can change. In my example country and level will always be the same as they represent the x pos.
This requires recursive approach as the strings stored in the str array, can be of any length. The longer the string the deeper nesting.

JSON (JavaScriptObjectNotation) is JavaScript. But JavaScript is not JSON. — DavidVollmers
– DavidVollmers, Commented Aug 27, 2015 at 12:12
@DavidVollmers Neither is the other. There are similarities, but one is a scripting language and the other is a data serialisation format. — Biffen
– Biffen, Commented Aug 27, 2015 at 12:14
I welcome your critique, I'm not an expert at this, and if you find something is not accurate, it would be nice if you've edited my question. Thank you. — Mantas
– Mantas, Commented Aug 27, 2015 at 12:19

Amir Popovich · Accepted Answer · 2015-08-27 12:20:41Z

1

This should work for you if the last level of your object is an array:

var str = [
"country.UK.level.1",
"country.UK.level.2",
"country.US.level.1",
"country.UK.level.3"
];

var obj = {};

str.forEach(function(str){
    var curr = obj;
    var splitted = str.split('.');
    var last = splitted.pop();
    var beforeLast = splitted.pop();

    splitted.forEach(function(sub){
        if(!curr.hasOwnProperty(sub))
        {
            curr[sub] = {};
        }

        curr = curr[sub];
    });

    if(!curr[beforeLast]){
        curr[beforeLast] = [];
    }
    curr[beforeLast].push(last);
})

console.log(obj);

JSFIDDLE.

answered Aug 27, 2015 at 12:20

Amir Popovich

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4 Comments

px5x2 Over a year ago

forEach call requires IE9+

Amir Popovich Over a year ago

@px5x2 - And? Whats the problem with that? The OP said nothing about IE < 9. And re-writing the code without a forEach will take about 30 seconds.

Mantas Over a year ago

From reading Eloquent JavaScript I learnt that forEach is much slower than an old-school for loop, with deep nesting as well.

px5x2 Over a year ago

@AmirPopovich nothing wrong, just wanted to state. Like we all write code completely unaware of browser compatibility.

Nina Scholz · Accepted Answer · 2015-08-27 13:23:27Z

1

This solution utilized a Array.prototype.forEach and Array.prototype.reduce.

var str = [
        "country.UK.level.1",
        "country.UK.level.2",
        "country.US.level.1",
        "country.UK.level.3"
    ],
    ordered = {};

str.forEach(function (a) {
    var aa = a.split('.'),
        val = aa.pop(),
        last = aa.length - 1;

    aa.reduce(function (obj, pro, i) {
        if (!(pro in obj)) {
            obj[pro] = i === last ? [] : {};
        }
        return obj[pro];
    }, ordered).push(val);
});
document.write('<pre>' + JSON.stringify(ordered, 0, 4) + '</pre>');

answered Aug 27, 2015 at 13:23

Nina Scholz

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