Currently, I am in the process of implementing a Stack in JavaScript using a LinkedList. However, I encountered an issue when trying to instantiate a Node class. When attempting to create a variable let newNode = new Node(x), I am receiving undefined.
I am unsure why this is happening and would like to gain clarity on the matter. By running new Node(x) in the repl, I get { val: -2, next: null } for a node. But as soon as I store it in a variable, like so: let newNode = new Node(x), it returns undefined when I try to console out newNode.
/**
* initialize your data structure here.
*/
var MinStack = function() {
this.size = 0;
this.min = null;
this.first = null;
};
var Node = function(val) {
this.val = val;
this.next = null;
}
/**
* @param {number} x
* @return {void}
*/
MinStack.prototype.push = function(x) {
if(this.first == null) {
this.first = new Node(x);
this.min = this.first;
this.size++;
return
}
let newNode = new Node(x);
if(newNode.val < this.min.val) {
this.min = newNode.val;
}
let oldFirst = this.first;
newNode.next = oldFirst;
this.first = newNode;
this.size++;
};
/**
* @return {void}
*/
MinStack.prototype.pop = function() {
if(this.first === null) {
return;
}
if(this.min === this.first) {
let current = this.first.next;
this.min = current;
while(current != null) {
if(current.val < this.min.val || this.size === 2) {
this.min = current;
}
current = current.next;
}
}
this.first = this.first.next;
this.size--;
return
};
/**
* @return {number}
*/
MinStack.prototype.top = function() {
return this.first.val;
};
/**
* @return {number}
*/
MinStack.prototype.getMin = function() {
return this.min.val;
};
// ["MinStack","push","push","push","getMin","pop","top","getMin"]
// [[],[-2],[0],[-3],[],[],[],[]]
var obj = new MinStack()
obj.push(-2)
obj.push(0)
obj.push(-3)
console.log(obj.getMin())
obj.pop();
obj.top();
obj.getMin();
This is the result at the debugger breakpoint:
> let newNode = new Node(x)
undefined
> newNode
undefined
> new Node(x)
{ val: 0, next: null }
I am puzzled by this inconsistency – what could be causing this?