update now implementation to be browser friendly

Author: dcottingham

packages/target-tools/src/fetchWithTelemetry.js

@@ -12,7 +12,7 @@ governing permissions and limitations under the License.
 */
 import https from "https";
 import http from "http";
-import { now } from "./perftool";
+import now from "./now";
 
 const PROTOCOL_MAP = {
   "http:": http.request,

packages/target-tools/src/now.js

@@ -0,0 +1,37 @@
+/* eslint-disable no-undef */
+import { isBrowser, isNodeJS, noop } from "./utils";
+import { now as defaultNow } from "./lodash";
+
+const NS_PER_SEC = 1e9;
+const MS_PER_NS = 1e6;
+
+let nodeJsNow = noop;
+
+function getNanoSeconds() {
+  const hr = process.hrtime();
+
+  return hr[0] * NS_PER_SEC + hr[1];
+}
+
+if (isNodeJS()) {
+  const upTime = process.uptime() * NS_PER_SEC;
+  const moduleLoadTime = getNanoSeconds();
+  const nodeLoadTime = moduleLoadTime - upTime;
+
+  // Same nano-precision implementation as performance-now lib
+  nodeJsNow = function () {
+    return (getNanoSeconds() - nodeLoadTime) / MS_PER_NS;
+  };
+}
+
+function getNowImpl() {
+  if (isBrowser()) {
+    if (window.performance && typeof window.performance.now === "function") {
+      return window.performance.now.bind(window.performance);
+    }
+    return defaultNow;
+  }
+  return nodeJsNow;
+}
+
+export default getNowImpl();

packages/target-tools/src/perftool.js

@@ -1,23 +1,6 @@
 /* eslint-disable import/prefer-default-export */
 import { isDefined, isUndefined } from "./utils";
-
-const NS_PER_SEC = 1e9;
-const MS_PER_NS = 1e6;
-
-function getNanoSeconds() {
-  const hr = process.hrtime();
-
-  return hr[0] * NS_PER_SEC + hr[1];
-}
-
-const UP_TIME = process.uptime() * NS_PER_SEC;
-const MODULE_LOAD_TIME = getNanoSeconds();
-const NODE_LOAD_TIME = MODULE_LOAD_TIME - UP_TIME;
-
-// Same nano-precision implementation as performance-now lib
-export function now() {
-  return (getNanoSeconds() - NODE_LOAD_TIME) / MS_PER_NS;
-}
+import now from "./now";
 
 export function createPerfToolInstance() {
   let timingIds = {};