Leet Code: min stack

var MinStack = function() {
    this.stack = [];
    this.min;
};

MinStack.prototype.push = function(x) {
    this.stack.push(x);
    if (!this.min && this.min !== 0) {
        this.min = x;
    } else if (x < this.min) {
        this.min = x;
    }
};


MinStack.prototype.pop = function() {
    let temp = this.stack.pop();
    this.min = this.stack[0];
    for (var i in this.stack) {
      this.min = Math.min(this.stack[i], this.min);
    }
};


MinStack.prototype.top = function() {
  return this.stack[this.stack.length - 1]  
};

MinStack.prototype.getMin = function() {
    return this.min;
};