How to convert flat JSON array into nested JSON with Google Apps Script?

Question

I have a standalone google script project. I'm getting a flat JSON answer from fetch via some API.Actually it should be nested but not. My JSON has level number instead nests. For example:

 [ { level: 1, first_name: 'Sammy', last_name: 'Snow', cloth_num: 8, cloth: null, color: null, day: null, sales: 1000}, { level: 2, first_name: null, last_name: null, cloth_num: 3, cloth: 'shirt', color: 'red', day: null, sales: 300}, { level: 3, first_name: null, last_name: null, cloth_num: 1, cloth: null, color: null, day: 1, sales: 100}, { level: 3, first_name: null, last_name: null, cloth_num: 2, cloth: null, color: null, day: 2, sales: 200}, { level: 2, first_name: null, last_name: null, cloth_num: 5, cloth: 'jeans', color: 'blue', day: null, sales: 700}, { level: 3, first_name: null, last_name: null, cloth_num: 2, cloth: null, color: null, day: 1, sales: 300}, { level: 3, first_name: null, last_name: null, cloth_num: 3, cloth: null, color: null, day: 2, sales: 400}, { level: 1, first_name: 'Danny', last_name: 'Crow', cloth_num: 15, cloth: null, color: null, day: null, sales: 2000}, { level: 2, first_name: null, last_name: null, cloth_num: 5, cloth: 't-shirt', color: 'red', day: null, sales: 800}, { level: 3, first_name: null, last_name: null, cloth_num: 3, cloth: null, color: null, day: 1, sales: 500}, { level: 3, first_name: null, last_name: null, cloth_num: 2, cloth: null, color: null, day: 2, sales: 300}, { level: 2, first_name: null, last_name: null, cloth_num: 5, cloth: 'hat', color: 'blue', day: null, sales: 700}, { level: 3, first_name: null, last_name: null, cloth_num: 2, cloth: null, color: null, day: 1, sales: 300}, { level: 3, first_name: null, last_name: null, cloth_num: 3, cloth: null, color: null, day: 2, sales: 400}, { level: 2, first_name: null, last_name: null, cloth_num: 5, cloth: 'socks', color: 'blue', day: null, sales: 500}, { level: 3, first_name: null, last_name: null, cloth_num: 2, cloth: null, color: null, day: 1, sales: 300}, { level: 3, first_name: null, last_name: null, cloth_num: 3, cloth: null, color: null, day: 2, sales: 200} ]

I wrote a script to nest second level into first level:

 function convertFlat(dataq) { let map = new Map() let x = dataq.forEach(x => {if (x.level === 1) x.next_level=[], map.set(x.first_name,x)}) for(let i = 0; i < dataq.length; i++){ if(dataq[i].level === 1) { l = map.get(dataq[i].first_name); continue; } else l.next_level.push(dataq[i]) } console.log([...map.values()]) }

How can I nest third level into second? I'm very new in Google Apps Script and have no idea how to repeat this loop for second and third level.

Answer 1

Couldn't resist myself... Here's my suggested code:

function unFlat(fj) {
  var arr=[];
  var objL1, objL2, objL3;
  var prev_level;
  for(var i=0; i<fj.length;i++) {
    var obj=fj[i];
    switch(obj.level) {
      case 3:
        objL3={};
        objL3.cloth_num=obj.cloth_num;
        objL3.day=obj.day;
        objL3.sales=obj.sales;
        objL2.items.push(objL3);
        prev_level=3;
        break;
      case 2:
        objL2={};
        objL2.cloth_num=obj.cloth_num;
        objL2.cloth=obj.cloth;
        objL2.color=obj.color;
        objL2.sales=obj.sales;
        objL2.items=[];
        objL1.cloths.push(objL2);
        prev_level=2;
        break;
      case 1:
        if(prev_level==3) arr.push(objL1);
        objL1={};
        objL1.first_name=obj.first_name;
        objL1.last_name=obj.last_name;
        objL1.cloth_num=obj.cloth_num;
        objL1.sales=obj.sales;
        objL1.cloths=[];
        prev_level=1;
        break;
    }
  }
  if(fj.length) arr.push(objL1);
  return arr;
}

arr will hold objects at the customer level,
objL1, objL2, objL3 hold info about custome, cloths, and items, respectively.
prev_level starts as undefined which is not 3 , and is for to know when to push cusotmer/ ObjL1 into arr .
Note: when we're done with the flat json, we need to push the un-pushed-yet-constructed last cusotmer/ ObjL1 - " if " there was any information at all.
In each case we collect the relevant properties, and push up one level into it's array.
Hope this makes sense!