获取 linter 错误“Unexpected token =”，对先前声明的变量进行解构赋值

Question

let data = []
let count, meta
if (req.params.id === 'count') {
  // get count only
} else {
  { data, count } = await myModel.find(filter, options)
  meta = { count }
}

gives me a linter error: "Parsing error: Unexpected token =" at the destructuring assignment. Is this just a setting in the linter config I need to change?

I can get rid of the error using parenthesis, but why is this required?

({ data, count } = await myModel.find(filter, options))

Answer 1

Any statement that begins with {... } will always be have the bracketed sequence parsed as a code block rather than as an object (including a destructuring object expression).

MDN clarifies this exact case in its documentation on destructuring :

 var a, b; ({a, b} = {a: 1, b: 2});

Notes: 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 var {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.