How to implement a set of stacks in JavaScript

JavaScript, Stacks, data structures

Here is one way to implement a data structure that allows for push and pop operations, pushing a new stack when a previous stack exceeds its capacity. Pop should remove a stack if the top stack is empty.

SetOfStacksTry in REPL
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function SetOfStacks(stackSize) {
  if (arguments.length < 1) throw new Error('You must provide a stack size limit as your first argument');
  this.stacks = [[]];
  this.max = stackSize;
}
SetOfStacks.prototype.push = function(value) {
  if (this.stacks[this.stacks.length-1].length >= this.max) {
    this.stacks.push([])
  }
  this.stacks[this.stacks.length-1].push(value);
};
SetOfStacks.prototype.pop = function() {
  const value = this.stacks[this.stacks.length-1].pop();
  if (this.stacks.length && this.stacks[this.stacks.length - 1].length === 0) {
    this.stacks.pop();
  }
  return value;
};
// this method is more complex than the rest
// if it's okay to have semi-full stacks in the middle, users may be surprised
SetOfStacks.prototype.popAt = function(stackNum) {
  if (stackNum < 1 || stackNum > this.stacks.length) {
    throw new Error('Invalid stack number');
  }
  if (stackNum === this.stacks.length) {
    return this.pop();
  }
  
  let stack = this.stacks[stackNum-1];
  let value = stack.pop();
  const tempStack = [];
  let nextStack;
  
  if (stackNum < this.stacks.length) {
    for (let i = stackNum; i < this.stacks.length; i++) {
      nextStack = this.stacks[i];
      while (nextStack.length) {
        tempStack.push(nextStack.pop());
      }
      stack.push(tempStack.pop());
      while (tempStack.length) {
        nextStack.push(tempStack.pop());
      }
      stack = nextStack;
    }
    if (this.stacks.length > 1 && this.stacks[this.stacks.length-1].length === 0) {
      this.stacks.pop();
    }
    
    return value;
  }
};

Tests can be found at REPL.it