Recursively create a nested array

Question

Any suggestions for how to recursively create a set of nested arrays / objects?

I am letting my users add multiple elements using a quick textarea. They will indicate sub items with an asterisk. So I have a string like this that I want to turn into an array.

level 1.1
level 1.2
* level 1.2.1
** level 1.2.1.1
** level 1.2.1.2
* level 1.2.2

This is the result I would like to see:

[
    {
        name: "level 1.1"
    },
    {
        name: "level 1.2",
        nodes: [
            {
                name: "level 1.2.1",
                nodes: [
                    {
                        name: "level 1.2.1.1"
                    },
                    {
                        name: "level 1.2.1.2"
                    }
                ]
            },
            {
                name: "level 1.2.2"
            }
        ]
    }
]

The challenge is that I don't know the depth that the nodes will go down to.

Any suggestions would be gratefully received.

Homework, ha! Brings back horrible memories from LONG ago. What's happening is that I'm giving people a chance to create multiple items at once through a text area, if they want something to be a nested item then they can add the asterisks. So the input data is as given. — Zagreus
– Zagreus, Commented Nov 27, 2017 at 8:53
@Zagreus Sounds like something that would leave a lot of room for user error. I'd suggest giving your users an interface for building the nested structure. — JLRishe
– JLRishe, Commented Nov 27, 2017 at 9:38

Nina Scholz · Accepted Answer · 2017-11-27 09:30:24Z

4

This is a linear approach, without recursion.

You could count the stars and take this information for the wanted level of the given node.

This proposal uses an array as reference to the last inserted level and maintains the wanted object structure.

This solution does not provide sanity checks, if a level is missing.

var data = ['level 1.1', 'level 1.2', '* level 1.2.1', '** level 1.2.1.1', '** level 1.2.1.2', '* level 1.2.2'],
    result = [],
    levels = [{ nodes: result }];

data.forEach(function (s) {
    var level = (s.match(/^\*+(?=\slevel)/) || [''])[0].length,
        name = s.match(/[^*]+$/)[0].trim();

    levels[level].nodes = levels[level].nodes || [];
    levels[level].nodes.push(levels[level + 1] = { name: name });
});

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Nov 27, 2017 at 9:30

answered Nov 27, 2017 at 9:18

Nina Scholz

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1 Comment

Zagreus Over a year ago

That's great thank you. If i understand it, you're using regex to work out how many *s there are. I will throw in a quick validation to make sure that there's no missed levels and I should be good to go.

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