How to parse JSON having nested arrays in javascript or jquery

Question

I want to parse JSON like below

{
   "nodeId":3892718504,
   "root":true,
   "subs":[
      {
         "nodeId":3892717286
      },
      {
         "nodeId":3892716092,
         "subs":[
            {
               "nodeId":3892715856,
               "subs":[
                  {
                     "nodeId":3892718592,
                     "subs":[
                        {
                           "nodeId":3892717580
                        }
                     ]
                  }
               ]
            }
         ]
      },
      {
         "nodeId":3892717497
      }
   ]
}

Each node can have subs and those subs can have nodes that can have their own subs. all I want is an array having all nodeId, how can I parse this JSON such that an array called nodes_list is populated with all nodeId. I can use javascript or jquery.

I'm trying the following approach to get an array of nodeId

jQuery.each(response.topology, function(i,obj) {
  if(i == "nodeId") {
    node_list.push(obj)
  }
  if(i == "subs"){
    jQuery.each(i, function(key,value) {
        if(i == "nodeId") {
            node_list.push(obj)
        }
    }
  }
});

I just need a little hint on how it can be in an iterative manner.

Answer 1

This can be done with function generators.

Perhaps not the most enjoyable approach, but I'm pretty sure the other solutions will already imply using other ways, so here is a solution using generators.

PS: Beware of browser support: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/yield

 const input = { "nodeId":3892718504, "root":true, "subs":[ { "nodeId":3892717286 }, { "nodeId":3892716092, "subs":[ { "nodeId":3892715856, "subs":[ { "nodeId":3892718592, "subs":[ { "nodeId":3892717580 } ] } ] } ] }, { "nodeId":3892717497 } ] }; function* nodeLookup(obj) { if (obj.nodeId) yield obj.nodeId; if (obj.subs) for (var i = 0; i < obj.subs.length; i++) yield *nodeLookup(obj.subs[i]); }; const node_ids = [...nodeLookup(input)]; console.log(node_ids); 

Answer 2

Just use recursion to iterate over subs

var nodeIds = [];
if (data.nodeId) nodeIds.push(data.nodeId);
function fetchNodeIds (subs) {
    if (!subs.length) return cb([]);
    var abc = [];
    subs.forEach(function (sub) {
        abc.push(sub.nodeId);
        if (sub.subs && sub.subs.length) abc = abc.concat(fetchNodeIds(sub.subs))
    });
    return abc;
}
nodeIds = nodeIds.concat(fetchNodeIds(data.subs));
console.log('--All nodeIds--', nodeIds)

Answer 3

It's straightforward to do recursively:

 const gatherIds = ({nodeId, subs}, results = []) => subs ? [...results, nodeId, ...(subs .flatMap (sub => gatherIds (sub, results) ))] : [...results, nodeId] const response = {"nodeId": 3892718504, "root": true, "subs": [{"nodeId": 3892717286}, {"nodeId": 3892716092, "subs": [{"nodeId": 3892715856, "subs": [{"nodeId": 3892718592, "subs": [{"nodeId": 3892717580}]}]}]}, {"nodeId": 3892717497}]} console .log ( gatherIds (response) ) 

If your target environments don't support flatmap , it's easy enough to shim.