Design an Ordered Stream LeetCode solution in JavaScript

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var OrderedStream = function (n) {
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  this.pointer = 0;
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  this.streamArray = new Array(n).fill(undefined);
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};
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OrderedStream.prototype.insert = function (idKey, value) {
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  this.streamArray[idKey - 1] = value;
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  if (this.streamArray[this.pointer] === undefined) {
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    return [];
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  } else {
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    const result = [];
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    while (this.streamArray[this.pointer] !== undefined) {
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      result.push(this.streamArray[this.pointer]);
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      this.pointer++;
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    }
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    return result;
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  }
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};