stack-tests.js

/**
 * Stack
 * LIFO data structure
 */

exports.Stack = Stack;
exports.Stack1 = Stack1;
exports.Stack2 = Stack2;
exports.Stack3 = Stack3;

function Stack() {
  this._top = new Entry(undefined, this._top);
}

Stack.prototype.peek = function () {
  return this._top.value;
};

Stack.prototype.pop = function () {
  var value = this._top.value;
  this._top = this._top.prev;
  return value;
};

Stack.prototype.push = function (value) {
  this._top = new Entry(value, this._top);
};

function Entry(value, prev) {
  this.value = value;
  this.prev = prev;
}

function Stack1() {
  var top = {value: undefined , prev: top};

  function pop() {
    var value = top.value;
    top = top.prev;
    return value;
  }

  function push(value) {
    top = {value: value , prev: top};
  }

  Object.defineProperty(this, 'pop', { value: pop });
  Object.defineProperty(this, 'push', { value: push });
}

function Stack2() {
  var stack = []
    , len = 0;

  function pop() {
    if (0 === len) return;
    len--;
    var value = stack[len];
    delete stack[len];
    return value;
  }

  function push(value) {
    stack[len] = value;
    len++;
  }

  Object.defineProperty(this, 'pop', { value: pop });
  Object.defineProperty(this, 'push', { value: push });
}

function Stack3() {
  var stack = []
    , len = 0;

  function pop() {
    return stack.pop();
  }

  function push(value) {
    stack.push(value);
  }

  Object.defineProperty(this, 'pop', { value: pop });
  Object.defineProperty(this, 'push', { value: push });
}