Update README.md

Author: yanglbme

solution/2600-2699/2666.Allow One Function Call/README.md

@@ -70,9 +70,10 @@ onceFn(4, 6, 8); // undefined, fn 没有被调用
 #### TypeScript
 
 ```ts
-function once<T extends (...args: any[]) => any>(
-    fn: T,
-): (...args: Parameters<T>) => ReturnType<T> | undefined {
+type JSONValue = null | boolean | number | string | JSONValue[] | { [key: string]: JSONValue };
+type OnceFn = (...args: JSONValue[]) => JSONValue | undefined;
+
+function once(fn: Function): OnceFn {
     let called = false;
     return function (...args) {
         if (!called) {
@@ -91,6 +92,32 @@ function once<T extends (...args: any[]) => any>(
  */
 ```
 
+#### JavaScript
+
+```js
+/**
+ * @param {Function} fn
+ * @return {Function}
+ */
+var once = function (fn) {
+    let called = false;
+    return function (...args) {
+        if (!called) {
+            called = true;
+            return fn(...args);
+        }
+    };
+};
+
+/**
+ * let fn = (a,b,c) => (a + b + c)
+ * let onceFn = once(fn)
+ *
+ * onceFn(1,2,3); // 6
+ * onceFn(2,3,6); // returns undefined without calling fn
+ */
+```
+
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