Insert Delete GetRandom O(1) LeetCode solution in JavaScript

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var RandomizedSet = function () {
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  this._data = [];
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  this._flatData = [];
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};
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RandomizedSet.prototype.hash = function (val) {
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  return val % 1e5;
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};
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RandomizedSet.prototype.insert = function (val) {
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  const hash = this.hash(val);
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  let basket = this._data[hash];
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  for (let i = 0; i < basket?.length; i++) {
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    if (basket[i][0] === val) {
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      return false;
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    }
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  }
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  if (!basket) {
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    this._data[hash] = [[val, this._flatData.length]];
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  } else {
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    this._data[hash].push([val, this._flatData.length]);
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  }
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  this._flatData.push(val);
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  return true;
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};
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RandomizedSet.prototype.remove = function (val) {
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  const hash = this.hash(val);
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  let basket = this._data[hash];
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  if (!basket) {
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    return false;
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  }
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  for (let i = 0; i < basket.length; i++) {
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    const currBasket = basket[i];
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    if (currBasket[0] === val) {
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      const idxInFlat = currBasket[1];
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      const reassignedValueInFlat = del(this._flatData, idxInFlat);
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      // Write new address in _data if needed
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      if (reassignedValueInFlat) {
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        this._data[this.hash(reassignedValueInFlat)].forEach((item) => {
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          if (item[0] === reassignedValueInFlat) {
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            item[1] = idxInFlat;
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            return; // from forEach
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          }
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        });
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      }
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      // Delete from _data
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      del(basket, i);
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      return true;
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    }
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  }
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  return false;
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};
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RandomizedSet.prototype.getRandom = function () {
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  return this._flatData[getRandomInt(0, this._flatData.length - 1)];
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};
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function getRandomInt(min, max) {
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  min = Math.ceil(min);
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  max = Math.floor(max);
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  return Math.floor(Math.random() * (max - min + 1)) + min;
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}
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function del(arr, idx) {
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  if (!arr.length) {
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    return null;
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  }
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  if (idx === arr.length - 1) {
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    arr.pop();
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    return null;
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  }
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  arr[idx] = arr.pop();
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  return arr[idx];
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}