4.4.js

"use strict";

function Stack() {
  this.dataStore = [];
  this.top = 0;
  this.push = push;
  this.pop = pop;
  this.peek = peek;
  this.length = length;
  this.clear = clear;
}

function push(element) {
  this.dataStore[this.top++] = element;
}

function pop(element) {
  return this.dataStore[--this.top];
}

function peek() {
  return this.dataStore[this.top-1];
}

function length() {
  return this.top;
}

function clear() {
  this.top = 0;
}


function  isPalindrome(word) {
  var s = new Stack();
  for(var i = 0; i < word.length; ++i) {
    s.push(word[i]);
  }

  var rword = "";
  while(s.length() > 0) {
    rword += s.pop();
  }

  if(word == rword) {
    return true;
  } else {
    return false;
  }
}

var word = 'hello';
if(isPalindrome(word)) {
  console.log(word + '是回文');
} else {
  console.log(word + '不是回文');
}

word = 'rececer';
if(isPalindrome(word)) {
  console.log(word + '是回文');
} else {
  console.log(word + '不是回文');
}