update javascript.md

Author: xiao-lix

articles/azure-monitor/app/javascript.md

@@ -214,7 +214,8 @@ Breaking changes in the SDK V2 version:
 - To allow for better API signatures, some of the API calls such as trackPageView, trackException have been updated. Running in IE8 or lower versions of the browser is not supported.
 - Telemetry envelope has field name and structure changes due to data schema updates.
 - Moved `context.operation` to `context.telemetryTrace`. Some fields were also changed (`operation.id` --> `telemetryTrace.traceID`)
-  - If you want to manually refresh the current pageview ID (for example, in SPA apps) this can be done with `appInsights.properties.context.telemetryTrace.traceID = Util.newId()`
+  - If you want to manually refresh the current pageview ID (for example, in SPA apps) this can be done with `appInsights.properties.context.telemetryTrace.traceID = Util.generateW3CId()`
+  > Note: Please update to use `Util.generateW3CId()` wherever you used `Util.newId()` before, in order to keep the traceID unique. Both will ultimately end up being the operation id.
 
 If you're using the current application insights PRODUCTION SDK (1.0.20) and want to see if the new SDK works in runtime, update the URL depending on your current SDK loading scenario.