155MinStack.js

// Time Complexity : O(1)
// Space Complexity : O(n)
// Did this code successfully run on Leetcode : Yes
// Any problem you faced while coding this : No

var MinStack = function () {
  this.mainStack = [];
  this.minStack = [];
};

/**
 * @param {number} val
 * @return {void}
 */
MinStack.prototype.push = function (val) {
  this.mainStack.push(val);
  const minVal =
    this.minStack.length === 0
      ? val
      : Math.min(val, this.minStack[this.minStack.length - 1]);
  this.minStack.push(minVal);
};

/**
 * @return {void}
 */
MinStack.prototype.pop = function () {
  this.mainStack.pop();
  this.minStack.pop();
};

/**
 * @return {number}
 */
MinStack.prototype.top = function () {
  return this.mainStack[this.mainStack.length - 1];
};

/**
 * @return {number}
 */
MinStack.prototype.getMin = function () {
  return this.minStack[this.minStack.length - 1];
};

/**
 * Your MinStack object will be instantiated and called as such:
 * var obj = new MinStack()
 * obj.push(val)
 * obj.pop()
 * var param_3 = obj.top()
 * var param_4 = obj.getMin()
 */