I have this code example:

var a = 10;
({a}) = 0;

In Google Chrome, it shows an error: SyntaxError: Invalid destructuring assignment target

In Firefox, it shows an error: ReferenceError: invalid assignment left-hand side

Actually, I would like to understand what kind of error it is?

I have this code example:

var a = 10;
({a}) = 0;

In Google Chrome, it shows an error: SyntaxError: Invalid destructuring assignment target

In Firefox, it shows an error: ReferenceError: invalid assignment left-hand side

Actually, I would like to understand what kind of error it is?

• javascript
• ecmascript-6

Share Improve this question Follow edited Mar 2, 2019 at 20:51 MaximPro asked Mar 2, 2019 at 20:49 MaximProMaximPro 54211 gold badge88 silver badges2424 bronze badges 10

• What did you expect that code to do? – Pointy Commented Mar 2, 2019 at 20:49
• @Pointy just testing the language – MaximPro Commented Mar 2, 2019 at 20:50
• 2 Well the language is telling you that that's wrong :) The ( ) are wrong, and the right-hand side is not an object so that's wrong too. – Pointy Commented Mar 2, 2019 at 20:52
• Because you're using an incorrect syntax: developer.mozilla/en-US/docs/Web/JavaScript/Reference/… – Terry Commented Mar 2, 2019 at 20:54
• It's still interesting that both browsers throw different errors. – Jonas Wilms Commented Mar 2, 2019 at 20:56

 |  Show 5 more ments

1 Answer 1

Sorted by: Reset to default 4

Well, it's simply invalid syntax. You are not allowed to put a destructuring pattern in parentheses^[1]:

It is an early Reference Error^[2] if LeftHandSideExpression is neither an ObjectLiteral nor an ArrayLiteral and IsValidSimpleAssignmentTarget of LeftHandSideExpression is false.

The ({a}) you have as a LeftHandSideExpression is a ParenthesizedExpression, not an ObjectLiteral, and the parenthesis don't contain a simple assignment target.

You probably are looking for a parenthesised statement to allow the destructuring pattern:

var a = 10;
({a} = 0);

_{1: Surprisingly, (a) = 0; is a valid statement though.
2: It seems that Chrome is wrong by throwing a SyntaxError then}