弯括号在本地反应

Question

In react native render function, I've tried writing something like:

render(){
  return (
    <View>
      {let a=5}
    </View>
  )
}

I thought I can write there any JS code, but it seems that it's an error. Can anyone explain why?

Answer 1

The problem is not related to ReactNative, but to JSX syntax.

You can only embed expressions in JSX . let a=5 is not an expression but an assignment, try to execute (let a = 5) in your browser console, you will see an error. You have to declare your variables above your JSX.

render(){
   let a = 5;
   return (
     <View>
      {/* use `a` here */}
     </View>
   )
}