Recursive function in javascript that outputs JSON

Question

In plain javascript, I am trying to create a function that will return a tree structure (json) of a folder, its subfolders and any files. I'm trying to achieve this using recursion. The problem with the below code is that it stops after the first recursive call.

I know that in JS you do references, and I need to create a new object that I pass the values from the previous call to, but I am struggling to do so.

function fun(file, json) {

  var tempJson = {
    'name' : json.name || '',
    'children' : obj.children || new Object()
  };

  if (file.type == 'file') {
    tempJson.type = 'file';
    tempJson.children = {}; // this will be empty, since there are no children
  } 
  else {
    tempJson.type = 'dir';
    var listed = file.listFiles();

    if (listed.length > 0) {
      for each (var item in listed) {
        tempJson.children = fun(item, tempJson);
      }
    } else {
      tempJson.children = {};
    }

  }
  return tempJson;
}

Example

From a directory structure like:

-root
--file1
--dir1
---file1.1
--dir2

I would like to get a json like:

{
name: 'root',
type: 'dir',
children : [
{
    name: 'file1',
    type: 'file',
    children: {}
},
{
    name: 'dir1',
    type: 'dir',
    children: 
    {
         name: 'file1.1',
         type: 'file',
         children: {},
    }
},
name: 'dir2',
type: 'dir',
children: {}
}

First call: var object = new Object(); fun(rootdir, object);

Hope this makes sense. Thanks!

For starters, you can't name your function function, but beyond that, you also aren't recursing at all. — Andrew
– Andrew, Commented Nov 6, 2019 at 22:27
@Andrew - Thanks for pointing it out. I just edited the name, it now reflects what I meant initially. — flaneur_o
– flaneur_o, Commented Nov 6, 2019 at 22:32

ibrahim mahrir · Accepted Answer · 2019-11-06 23:06:55Z

1

As pointed out in the comments, children should be an array:

function fun(entry) {
  var entryObj = {                                         // construct the object for this entry
    name: entry.name || "",
    type: entry.type,                                      // put the type here instead of using an if
    children: []                                           // children must be an array
  };

  if(entry.type === "dir") {                               // if this entry is a directory
    var childEntries = entry.listFiles();                  // get its child entries
    for(var childEntry of childEntries) {                  // and for each one of them
      entryObj.children.push(fun(childEntry));             // add the result of the call of 'fun' on them to the children array
    }
  }

  return entryObj;
}

Then call it like so:

var tree = fun(rootEntry);

edited Nov 6, 2019 at 23:06

answered Nov 6, 2019 at 22:47

ibrahim mahrir

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2 Comments

Brandon Hill Over a year ago

This is close, but should be modifying obj (currently unused) not creating new entryObj. Either that or there's no need to accept obj.

ibrahim mahrir Over a year ago

@BrandonHill good point. I'll edit, thanks. I got rid of it alltogether.

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