Javascript：分配一个变量并同时检查是否为假

Question

Is there a way in javascript to both assign and check for undefined (or null or whatever) in one line like this:

if (let myVar = DoSomethingAndReturnValue()) {
    // DoSomethingAndReturnValue() returned a falsy value and so myVar is falsy
   return
}
// myVar is now assigned with some value we can do something with it.

Answer 1

This creates a global variable but does it.

if (!(myVar = DoSomethingAndReturnValue())) {
   console.log(2);
}