I read the following code here:
({ a, b } = { a: 10, b: 20 });
console.log(a); // 10
console.log(b); // 20
What is the difference between that and the following:
{ a, b } = { a: 10, b: 20 };
console.log(a); // 10
console.log(b); // 20
Considering that they have the same outcome.
P.S. The point is the parentheses around the assignment expression
Your second example shouldn't work. You should see an error.
let a, b;
{ a, b } = { a: 10, b: 20 };
// Uncaught SyntaxError: Unexpected token '='
The reason is that the curly brackets { a, b } are considered a block not an object literal.
// This is a block
{
console.log('Hello world');
}
When surounded by parentheses it's considered an object literal
({ hello: world })
Note: The parentheses ( ... ) around the assignment statement are required when using object literal destructuring assignment without a declaration.
{a, b} = {a: 1, b: 2} is not valid stand-alone syntax, as the {a, b} on the left-hand side is considered a block and not an object literal.
However, ({a, b} = {a: 1, b: 2}) is valid, as is const {a, b} = {a: 1, b: 2}
Your ( ... ) expression needs to be preceded by a semicolon or it may be used to execute a function on the previous line.