Stack
A simple data structure that stores elements as on a physical stack: The first element inserted is the last to be extracted (FILO).
function Stack() {
var top = 0,
elements = [];
this.stackEmpty = function() {
return (top === 0);
};
this.push = function(e) {
elements[++top] = e;
};
this.pop = function() {
return (this.stackEmpty()) ? null : elements[top--];
};
}