Add duration property to Stopwatch class

Author: qz2017

apps/rush-lib/src/utilities/Stopwatch.ts

@@ -81,12 +81,7 @@ export class Stopwatch {
     if (this._state === StopwatchState.Stopped && this._startTime === undefined) {
       return '0.00 seconds (stopped)';
     }
-
-    const curTime: number = this._endTime !== undefined
-      ? this._endTime
-      : this._getTime();
-
-    const totalSeconds: number = ((curTime - this._startTime) / 1000.0);
+    const totalSeconds: number = this._getTotalSeconds();
 
     if (totalSeconds > 60) {
       const minutes: number = Math.floor(totalSeconds / 60);
@@ -98,4 +93,22 @@ export class Stopwatch {
       return `${totalSeconds.toFixed(2)} seconds`;
     }
   }
+
+  /**
+   * Get the duration in seconds.
+   */
+  public get duration(): number {
+    return this._getTotalSeconds();
+  }
+
+  private _getTotalSeconds(): number {
+    if (this._startTime === undefined) {
+      return 0;
+    }
+    const curTime: number = this._endTime !== undefined
+      ? this._endTime
+      : this._getTime();
+
+    return ((curTime - this._startTime) / 1000.0);
+  }
 }

apps/rush-lib/src/utilities/test/Stopwatch.test.ts

@@ -54,12 +54,14 @@ describe('Stopwatch', () => {
     watch.start();
     watch.reset();
     assert.equal(watch.toString(), '0.00 seconds (stopped)');
+    assert.equal(watch.duration, 0);
     done();
   });
 
   it('gives 0.00 seconds when not running', (done: MochaDone) => {
     const watch: Stopwatch = new Stopwatch();
     assert.equal(watch.toString(), '0.00 seconds (stopped)');
+    assert.equal(watch.duration, 0);
     done();
   });
 
@@ -103,4 +105,26 @@ describe('Stopwatch', () => {
     assert.equal(watch.toString(), '1 minute 1.3 seconds');
     done();
   });
+
+  it('uses the latest time when the clock is not stopped', (done: MochaDone) => {
+    const watch: Stopwatch = new Stopwatch(pseudoTimeSeconds([0, 1, 2]));
+    watch.start();
+    assert.equal(watch.toString(), '1.00 seconds');
+    assert.equal(watch.toString(), '2.00 seconds');
+    done();
+  });
+
+  it('returns duration when the clock is stopped', () => {
+    const watch: Stopwatch = new Stopwatch(pseudoTimeSeconds([0, 61.25]));
+    watch.start();
+    watch.stop();
+    assert.equal(watch.duration, 61.25);
+  });
+
+  it('returns duration using the latest time when the clock is not stopped', () => {
+    const watch: Stopwatch = new Stopwatch(pseudoTimeSeconds([0, 1, 2]));
+    watch.start();
+    assert.equal(watch.duration, 1);
+    assert.equal(watch.duration, 2);
+  });
 });

common/reviews/api/rush-lib.api.ts

@@ -271,6 +271,7 @@ module RushConstants {
 class Stopwatch {
   // (undocumented)
   constructor(getTime: () => number = Utilities.getTimeInMs);
+  public readonly duration: number;
   public reset(): Stopwatch;
   public static start(): Stopwatch;
   // (undocumented)