How to destructure an object to an already defined

问题:

This question already has answers here:

object destructuring without var (2 answers)

Closed 4 years ago.

The following produces a syntax error:

let source,
    screenings,
    size;

source = {
    screenings: 'a',
    size: 'b'
};

{
    screenings,
    size
} = source;

Expected result:

screenings should be equal to 'a'
size should be equal to 'b'

回答1:

You need to use assignment without declaration syntax:

({
    screenings,
    size
} = source);

Babel REPL Example

From the linked docs:

The ( .. ) around the assignment statement is required syntax when using object literal destructuring assignment without a declaration

And obviously you need to use this as you can't redeclare a let variable. If you were using var, you could just redeclare var { screenings, size } = source;