React StrictMode calls all Effects twice to make sure their cleanup/unmount handlers work as intended. You may need to change your effects accordingly, even if they have an empty dependency list and would normally not unmount before the site is closed. Note, this only happens in Strict + development mode. In a production build, effects … Read more
In index.js change <React.StrictMode><App /><React.StrictMode> to <App /> and you will not see this warning. Please note that strict mode helps you with Identifying components with unsafe lifecycles Warning about legacy string ref API usage Warning about deprecated findDOMNode usage Detecting unexpected side effects Detecting legacy context API Please refer to https://reactjs.org/docs/strict-mode.html before removing it.
No, you can’t disable strict mode per function. It’s important to understand that strict mode works lexically; meaning — it affects function declaration, not execution. Any function declared within strict code becomes a strict function itself. But not any function called from within strict code is necessarily strict: (function(sloppy) { “use strict”; function strict() { … Read more
Its main purpose is to do more checking. Just add “use strict”; at the top of your code, before anything else. For example, blah = 33; is valid JavaScript. It means you create a completely global variable blah. But in strict mode it’s an error because you did not use the keyword “var” to declare … Read more