How to implement a stack using javascript

stack.js

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

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

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

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

	function length() {
		return this.top;
	}

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

// test Stack
/*
var s = new Stack();
s.push('ada');
s.push('bob');
s.push('cook');
s.push('david');
console.log("length is: " + s.length());
console.log(s.peek());
var poped = s.pop();
console.log("the poped element is: " + poped);
console.log(s.peek());
s.clear();
console.log("after clear length is: " + s.length());
console.log(s.peek());
s.push('erik');
console.log(s.peek());
*/

// convert base
// convert 50 to base 2
// 将10进制转换成2进制，使用stack

function mulBase(num, base) {
	var s = new Stack()	;
	do {
		s.push(num % base);
		num = Math.floor(num /= base);
	} while(num > 0);
	var converted = '';
	while(s.length() > 0) converted += s.pop();
	return converted;
}
console.log("50 convert to base 2 is ");
console.log(mulBase(50, 2));
console.log("");
// 实现回文检测
// test palindrome

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 + " is palindrome");
else
	console.log(word + " is not palindrome");

var word = "racecar";
if(isPalindrome(word))
	console.log(word + " is palindrome");
else
	console.log(word + " is not palindrome");

// simulating recursive process
function fact(n) {
	var s = new Stack();
	while(n > 1) s.push(n--);

	var product = 1;
	while(s.length() > 0) product *= s.pop();

	return product;
}

// is miss parenthesis

function isParenthesisMissing(expression) {
	var s = new Stack();
	var position = 0;
	for(var i = 0; i < expression.length; i++) {
		position = i + 1;
		if(expression[i] == '(') s.push(position);
		if(expression[i] == ')') s.pop();
	}
	var result = '';
	if (s.length() !== 0) {
		while(s.length() > 0) result = result + s.pop() + ' ';
	}		
	return result;
}

var expression = '2.3 + 23 / 12 + (3.14159 * .24';
console.log(isParenthesisMissing(expression));