Update README.md

Author: yanglbme

solution/0700-0799/0719.Find K-th Smallest Pair Distance/README.md

@@ -226,6 +226,43 @@ function smallestDistancePair(nums: number[], k: number): number {
 }
 ```
 
+#### JavaScript
+
+```js
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ */
+function smallestDistancePair(nums, k) {
+    nums.sort((a, b) => a - b);
+    const n = nums.length;
+    let left = 0,
+        right = nums[n - 1] - nums[0];
+
+    while (left < right) {
+        const mid = (left + right) >> 1;
+        let count = 0,
+            i = 0;
+
+        for (let j = 0; j < n; j++) {
+            while (nums[j] - nums[i] > mid) {
+                i++;
+            }
+            count += j - i;
+        }
+
+        if (count >= k) {
+            right = mid;
+        } else {
+            left = mid + 1;
+        }
+    }
+
+    return left;
+}
+```
+
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