Detect Loop in Linked List

detect-loop-linked-list.js

var hasCycle = function(head) {
    
    if (head === null) return false;
    
    if (head.next === null) return false;
    
    let slow = head;
    let fast = head.next;
    
    while(fast !== null && fast.next !== null){
        slow = slow.next;
        fast = fast.next.next;
        
        if(slow === fast) {
            return true;
        }
    }
    
    return false;
    
};