Merge Two Sorted Lists.js

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var mergeTwoLists = function(l1, l2) {
    if(!l1) return l2;
    if(!l2) return l1;
    if(l1.val <= l2.val){
    	l1.next = mergeTwoLists(l1.next, l2);
    	return l1;
    }
    else{
    	l2.next = mergeTwoLists(l2.next, l1);
    	return l2;
    }
}