APM (Application Performance Management)

The heart of APM solutions is understanding why transactions in your application are slow or failing.

10 Critical Application Performance Management Features for Developers

1. Performance of every web request and transaction
2. Code level performance profiling
3. Usage and performance of all application dependencies like databases, web services, caching, etc (Distributed Tracing)
4. Detailed traces of individual web requests or transactions
5. Basic server monitoring and metrics like CPU, memory, etc
6. Application framework metrics like performance counters, JMX MBeans, etc
7. Custom applications metrics created by the developer team or business (tracking, reporting, alerting)
8. Application log data
9. Application errors
10. Real user monitoring (RUM)

Here's a list of New Relic Alternatives/Replacements of 2019:

1. AppOptics
2. Pingdom Server Monitor (formerly Scout App)
3. Stackify Retrace
4. DynaTrace (formerly Ruxit)
5. Atatus
6. Datadog
7. LogicMonitor
8. AppDynamics
9. Elastic APM

For me, I care about where is slow and why it is slow with prompt alerting support.

Javascript memory leak

Here are some links talking about Javascript memory leak.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Memory_Management
http://javascript.info/tutorial/memory-leaks
http://stackoverflow.com/questions/12772822/javascript-memory-usage-management
http://www.javascriptkit.com/javatutors/closuresleak/index3.shtml

http://dmitrysoshnikov.com/ecmascript/es5-chapter-3-1-lexical-environments-common-theory/#static-lexical-scope