3-1.js

function Stack() {
  var data = [];
  var stackPtr = [0,0,0];
  this.push = function(stackNumber, d) {
    var index = stackNumber + stackPtr[stackNumber] * 3;
    data[index] = d;
    stackPtr[stackNumber]++;
  };
  this.print = function() {
    var strs = ["","",""];
    for (var i = 0; i < data.length; i++) {
      console.log(i);
      stack = i % 3;
      if(data[i]) {
        strs[stack] = strs[stack] + " " + data[i];
      }
    }
    console.log("Stack 0:" + strs[0]);
    console.log("Stack 1:" + strs[1]);
    console.log("Stack 2:" + strs[2]);
  };
}
      


var s = new Stack();
s.push(0, 5);
s.push(0, 2);
s.push(0, 1);
s.push(2, 1);
s.push(2, 1);
s.push(2, 1);
s.push(1, 2);
s.push(1, 2-1);
s.print();