JSFiddle - React, Tailwind, and code Playground

JavaScript

var data = [{
  "_id": "1",
  "parentId": "thisPostId",
  "topLevelId": "1",
  "text": "<p>comment</p>",
}, {
  "_id": "2",
  "parentId": "1",
  "topLevelId": "1",
  "text": "<p>reply to comment</p>",
}, {
  "_id": "3",
  "parentId": "2",
  "topLevelId": "1",
  "text": "<p>reply to reply to comment</p>",
}, {
  "_id": "4",
  "parentId": "3",
  "topLevelId": "1",
  "text": "<p>reply to reply to reply to comment</p>",
}];
var getIndex = function(_id) {
  for (var i = 0; i < data.length; i++) {
    if (data[i]._id == _id) {
      return i;
    }
  }
};

function deepCopy(obj) {
   if (null == obj || "object" != typeof obj) return obj;
    var copy = obj.constructor();
    for (var attr in obj) {
        if (obj.hasOwnProperty(attr)) copy[attr] = obj[attr];
    }
    return copy;
}
var _id = 4;

var index = getIndex(_id);
var _temp = deepCopy(data);
var removedData = data.splice(index, 1);
console.log(removedData);
if (typeof index !== 'undefined') {
  var neededData = _temp.splice(index, (_temp.length - index));
  console.log(neededData);
}