Maximum Frequency Stack LeetCode solution in JavaScript

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var FreqStack = function () {
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  //hashMap to keep track of the values being repeated
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  this.frequencyMap = {};
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  //List map to keep track of the sequence of the value being entered
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  this.listMap = {};
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  //Max Frequency variable to keep track of the max frequency
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  this.maxValueFrequency = 0;
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};
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/**
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 * @param {number} val
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 * @return {void}
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 */
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FreqStack.prototype.push = function (val) {
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  //if the hashMap doesn't have value being pushed then make a entry to it with 1 else increament by 1
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  this.frequencyMap[val] = this.frequencyMap[val]
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    ? this.frequencyMap[val] + 1
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    : 1;
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  //get the frequency of the value being pushed
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  const currentValueFrequency = this.frequencyMap[val];
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  //check if the current frequency is max or itself
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  this.maxValueFrequency = Math.max(
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    this.maxValueFrequency,
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    currentValueFrequency
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  );
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  //if current value frequency is not in the listmap then make a new entry else push it
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  if (!this.listMap[currentValueFrequency])
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    this.listMap[currentValueFrequency] = [val];
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  else this.listMap[currentValueFrequency].push(val);
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};
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/**
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 * @return {number}
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 */
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FreqStack.prototype.pop = function () {
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  //make a temporary list of the max value frequency
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  const tempList = this.listMap[this.maxValueFrequency];
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  //get the last element from the temporary list
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  const top = tempList[tempList.length - 1];
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  //remove the item from the list
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  tempList.pop();
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  //update the list
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  this.listMap[this.maxValueFrequency] = tempList;
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  //if the popped item exist in the frequecy map then decrease it by 1
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  if (this.frequencyMap[top]) this.frequencyMap[top]--;
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  //if the max value frequency in the listmap is blank then reduce the maxValueFrequency;
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  if (this.listMap[this.maxValueFrequency].length === 0)
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    this.maxValueFrequency--;
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  //return the max value frequency with proper order if it is same
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  return top;
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};
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//Time O(Log n) // for both Push and Pop
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//Space O(n) for storing all the values in the hashMap and listMap