Traverse all the Nodes of a JSON Object Tree with JavaScript

Question

I\'d like to traverse a JSON object tree, but cannot find any library for that. It doesn\'t seem difficult but it feels like reinventing the wheel.

In XML there are

Answer 1

Depends on what you want to do. Here's an example of traversing a JavaScript object tree, printing keys and values as it goes:

function js_traverse(o) {
    var type = typeof o 
    if (type == "object") {
        for (var key in o) {
            print("key: ", key)
            js_traverse(o[key])
        }
    } else {
        print(o)
    }
}

js> foobar = {foo: "bar", baz: "quux", zot: [1, 2, 3, {some: "hash"}]}
[object Object]
js> js_traverse(foobar)                 
key:  foo
bar
key:  baz
quux
key:  zot
key:  0
1
key:  1
2
key:  2
3
key:  3
key:  some
hash

Answer 2

My Script:

op_needed = [];
callback_func = function(val) {
  var i, j, len;
  results = [];
  for (j = 0, len = val.length; j < len; j++) {
    i = val[j];
    if (i['children'].length !== 0) {
      call_func(i['children']);
    } else {
      op_needed.push(i['rel_path']);
    }
  }
  return op_needed;
};

Input JSON:

[
    {
        "id": null, 
        "name": "output",   
        "asset_type_assoc": [], 
        "rel_path": "output",
        "children": [
            {
                "id": null, 
                "name": "output",   
                "asset_type_assoc": [], 
                "rel_path": "output/f1",
                "children": [
                    {
                        "id": null, 
                        "name": "v#",
                        "asset_type_assoc": [], 
                        "rel_path": "output/f1/ver",
                        "children": []
                    }
                ]
            }
       ]
   }
]

Function Call:

callback_func(inp_json);

Output as per my Need:

["output/f1/ver"]

Answer 3

We use object-scan for all our data processing needs now. It's very powerful once you wrap your head around it. Here is how you could do basic traversal

const objectScan = require('object-scan');

const obj = {
  foo: 'bar',
  arr: [1, 2, 3],
  subo: {
    foo2: 'bar2'
  }
};

objectScan(['**'], {
  filterFn: ({ key, value }) => {
    console.log(key, value);
  }
})(obj);
/* =>
[ 'subo', 'foo2' ] 'bar2'
[ 'subo' ] { foo2: 'bar2' }
[ 'arr', 2 ] 3
[ 'arr', 1 ] 2
[ 'arr', 0 ] 1
[ 'arr' ] [ 1, 2, 3 ]
[ 'foo' ] 'bar'
*/

Answer 4

I wanted to use the perfect solution of @TheHippo in an anonymous function, without use of process and trigger functions. The following worked for me, sharing for novice programmers like myself.

(function traverse(o) {
    for (var i in o) {
        console.log('key : ' + i + ', value: ' + o[i]);

        if (o[i] !== null && typeof(o[i])=="object") {
            //going on step down in the object tree!!
            traverse(o[i]);
        }
    }
  })
  (json);