javascript如何分配参考值？

Question

I am learning react and i was using react-router-dom library to change the routes of the project. So i added from the library and added history to it. And added createBrowserHistory from npm package history .

<Router history={createBrowserHistory()}>

But it was not changing the routes and was generating a warning.

You cannot change <Router history>

then i changed it to and then passed in Router

const history = createBrowserHistory()
<Router history={history}>

Passing the browser history to a variable worked. Why was this happening? Is this some concept of Javascript ?

Answer 1

I'm not sure but I think main problem here could be related to the scope of variable. While you creating object inside of jsx it will be stored inside of Router component and maybe react needs to have it accessible outside of it. (For example when history changes react knows that it should rerender component)

But anyway if you are beginner you don't need to use Router component, check BrowserRouter https://reacttraining.com/react-router/web/api/Route