js实现栈

<script type="text/javascript">
function Stack() 
{
this. dataStore = [] ;
this. top = 0;
this. push = push;
this. pop = pop;
this. peek = peek;
this. clear = clear;
this. length = length;
}
function push(element) 
{
this. dataStore[this. top++] = element;
}
function peek() 
{
return this. dataStore[this. top- 1] ;
}
function pop() 
{
return this. dataStore[- - this. top] ;
}
function clear() 
{
this. top = 0;
}
function length() 
{
return this. top;
}
function doTest()
{
	var s = new Stack();
	s. push(" David" );
	s. push(" Raymond" );
	s. push(" Bryan" );
	document.write(" length: " + s. length());
	document.write(s. peek());
	var popped = s. pop();
	document.write(" The popped element is: " + popped);
	document.write(s. peek());
	s. push(" Cynthia" );
	document.write(s. peek());
	s. clear();
	document.write(" length: " + s. length());
	document.write(s. peek());
	s. push(" Clayton" );
	document.write(s. peek());
}
</script>