let data = [ {ilvl: "0", numId: "1", text: "Sdvs"},
 {ilvl: "0", numId: "1", text: "verFFE"},
 {ilvl: "1", numId: "1", text: "235rf"},
 {ilvl: "0", numId: "2", text: "Hrg"},
 {ilvl: "1", numId: "2", text: "Gtegwr"},
 {ilvl: "1", numId: "2", text: "ser"}];

let obj = {};
data.forEach(row => {
   if (!obj[row.numId]) obj[row.numId] = {};
   if (!obj[row.numId][row.ilvl]) obj[row.numId][row.ilvl] = [];
   obj[row.numId][row.ilvl].push(row.text);
});


let result = Object.keys(obj).map(numId => 
  ({
    numId, 
    levels: Object.keys(obj[numId]).map(ilvl => ({
      ilvl, 
      children: obj[numId][ilvl].map(text => ({text}))
    })) 
  })
);

console.log(result);