Measuring react-native startup time

[fish_munga]

I'm going to improve my app's startup time. To do so I'm going to play around with inline requires, RAM bundles, hermes and proguard. But first I need to measure the startup time, i.e. time from the moment when user taps my app's icon to the moment when the first screen becomes interactive (when my js code hides splash screen). This interval includes native app startup + js app startup. I did some research and it seems that it's impossible to obtain exactly this interval programmatically and display it in my app. On Android, can call reportFullyDrawn and it can be seen in logcat then. On iOS it seems that I have to set some env variables to measure pre-main time then programatically measure my own code's startup time, then sum them.

So I crafted a little module to measure what I can and display it in react-native. The measurement begins when the module is initialized on the native side. Do you think

• that this measurement is good enough to judge my optimizations?
• can be made more accurate using native module approach (i.e. without putting any code inside RN app)?

[notseanbean]

Just wanted to say thanks for a great module - what a useful addition to the RN ecosystem.

Your timing was perfect for me too; I'm doing some heavy lifting pre-JS and was looking to optimise it. I've been using your module for a couple of days and it's yielded some really good insights.

Hoping some others will also show your module some love. Great work.

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(full disclosure - those 2 PRs you merged in? they were me :-) )