feat: add js solution to lc problem: No.1701 (doocs#3238)

Author: rain84

solution/1700-1799/1701.Average Waiting Time/README.md

@@ -161,6 +161,19 @@ function averageWaitingTime(customers: number[][]): number {
 }
 ```
 
+#### JavaScript
+
+```js
+function averageWaitingTime(customers) {
+    let [tot, t] = [0, 0];
+    for (const [a, b] of customers) {
+        t = Math.max(t, a) + b;
+        tot += t - a;
+    }
+    return tot / customers.length;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/1700-1799/1701.Average Waiting Time/README_EN.md

@@ -159,6 +159,19 @@ function averageWaitingTime(customers: number[][]): number {
 }
 ```
 
+#### JavaScript
+
+```js
+function averageWaitingTime(customers) {
+    let [tot, t] = [0, 0];
+    for (const [a, b] of customers) {
+        t = Math.max(t, a) + b;
+        tot += t - a;
+    }
+    return tot / customers.length;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/1700-1799/1701.Average Waiting Time/Solution.js

@@ -0,0 +1,8 @@
+function averageWaitingTime(customers) {
+    let [tot, t] = [0, 0];
+    for (const [a, b] of customers) {
+        t = Math.max(t, a) + b;
+        tot += t - a;
+    }
+    return tot / customers.length;
+}