backo2: expose properties, improve docs (#38451)

types/backo2/backo2-tests.ts

@@ -10,4 +10,9 @@ const backoff3 = new Backoff({
 });
 
 const y: number = backoff3.duration();
+const attempts: number = backoff3.attempts;
+const min: number = backoff3.ms;
+const max: number = backoff3.max;
+const jitter: number = backoff3.jitter;
+const factor: number = backoff3.factor;
 backoff3.reset();

types/backo2/index.d.ts

@@ -14,17 +14,40 @@ type BackoffOptions = Partial<{
 declare class Backoff {
     constructor(opts?: BackoffOptions);
 
+    /**
+     * The number of previous attempts
+     */
+    attempts: number;
+    /**
+     * A lower bound on the duration between attempts
+     */
+    ms: number;
+    /**
+     * An upper bound on the duration between attempts
+     */
+    max: number;
+    /**
+     * An upper bound on the variance around the duration between attempts
+     */
+    jitter: number;
+    /**
+     * The base to which the attempt is raised as an exponent
+     */
+    factor: number;
+    /**
+     * Compute the backoff duration and increment the number of attempts
+     */
     duration(): number;
     /**
-     * Reset the number of attempts.
+     * Reset the number of attempts
      */
     reset(): void;
     /**
-     * Set the minimum duration
+     * Set the minimum duration between attempts
      */
     setMin(min: number): void;
     /**
-     * Set the maximum duration
+     * Set the maximum duration between attempts
      */
     setMax(max: number): void;
     /**