Merge pull request #1001 from xiaofei-2020/ts1

添加（链表理论基础.md）：增加JS和TS版本

problems/0203.移除链表元素.md

@@ -302,7 +302,63 @@ var removeElements = function(head, val) {
 };
 ```
 
+TypeScript:
+
+版本一（在原链表上直接删除）：
+
+```typescript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     val: number
+ *     next: ListNode | null
+ *     constructor(val?: number, next?: ListNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.next = (next===undefined ? null : next)
+ *     }
+ * }
+ */
+function removeElements(head: ListNode | null, val: number): ListNode | null {
+    // 删除头部节点
+    while (head !== null && head.val === val) {
+        head = head.next;
+    }
+    if (head === null) return head;
+    let pre: ListNode = head, cur: ListNode = head.next;
+    // 删除非头部节点
+    while (cur) {
+        if (cur.val === val) {
+            pre.next = cur.next;
+        } else {
+            pre = pre.next;
+        }
+        cur = cur.next;
+    }
+    return head;
+};
+```
+
+版本二（虚拟头节点）：
+
+```typescript
+function removeElements(head: ListNode | null, val: number): ListNode | null {
+    head = new ListNode(0, head);
+    let pre: ListNode = head, cur: ListNode = head.next;
+    // 删除非头部节点
+    while (cur) {
+        if (cur.val === val) {
+            pre.next = cur.next;
+        } else {
+            pre = pre.next;
+        }
+        cur = cur.next;
+    }
+    return head.next;
+};
+```
+
 Swift：
+
 ```swift
 /**
  * Definition for singly-linked list.

problems/链表理论基础.md

@@ -168,6 +168,32 @@ public class ListNode {
 }
 ```
 
+JavaScript:
+
+```javascript
+class ListNode {
+  val;
+  next = null;
+  constructor(value) {
+    this.val = value;
+    this.next = null;
+  }
+}
+```
+
+TypeScript:
+
+```typescript
+class ListNode {
+  public val: number;
+  public next: ListNode = null;
+  constructor(value: number) {
+    this.val = value;
+    this.next = null;
+  }
+}
+```
+
 Python：