JavaScript interview questions and answers

The effect starts after paint, fetch is scheduled, and the function yields at await so React can keep working.

I reproduce by changing filters quickly and logging request ids.

I use a status field like idle, loading, success, error and narrow with a switch.

Interfaces with the same name in the same scope merge their members, which is useful for extending libraries.

When fetch uses credentials include, the server cannot reply Access-Control-Allow-Origin star.

They can serve shell HTML and assets offline, which is great for PWAs.

Synchronous logs run first.

Class Foo still has Foo.prototype and instances link to it.

In the effect I create a controller, pass signal to fetch, and abort in cleanup.

ReactNode covers strings, numbers, fragments, and elements, which is what most layout components accept.

It is the work from HTML and CSS bytes to pixels: parse, CSSOM, render tree, layout, paint.

Leading runs immediately, then ignores calls until the window ends

As const on a route name array makes a union of literal strings instead of string.

I take heap snapshots before and after visiting a route twice and look for detached DOM nodes or growing arrays.