Using return as one of multiple statements in ternary expression [duplicate]

问题

This question already has answers here:

Why can't we have return in the ternary operator? (4 answers)

Closed 8 months ago.

I have this code:

  err ? (reject(err), return)
      : resolve(db)

Which returns:

SyntaxError: Unexpected token return

However this works:

err ? (reject(err), console.log('test'))
    : resolve(db)

Why is that return can't be used in this situation? Is there other alternative to stop function execution while using ternary operator for multiple statements?

回答1:

It's a ternary expression, the expression as a whole must evaluate to a value, and thus contain only expressions.

You can't say a = 1 + return; either.

Is there other alternative to stop function execution while using ternary operator for multiple statements?

The if statement...

if (err) { reject(err); return }

resolve(db);

回答2:

err ? (reject(err), return)
    : resolve(db)

Is there other alternative to stop function execution while using ternary operator for multiple statements?

Ternary operators are not like if else in the sense of including an implicit return statement. So in order to return asap once the condition satisfies, you might properly do as follows.

return err ? reject(err)
           : resolve(db);

来源：https://stackoverflow.com/questions/39895655/using-return-as-one-of-multiple-statements-in-ternary-expression