Why javascript object de-structuring is not working?

Asked Mar 31 '20 at 16:20

Active Mar 31 '20 at 16:20

Viewed 32 times

I tried to de-structure a object in javascript as following

Example #1

var a, b
var hello = {
  a: 1,
  b: 3
}

({a, b} = hello);
console.log(a);

If you hit Run code snippet you will encounter

{ "message": "Uncaught TypeError: Cannot destructure property 'a' of 'hello' as it is undefined.", "filename": "https://stacksnippets.net/js", "lineno": 18, "colno": 3 }

Example #2

var a, b
var hello = {
  a: 1,
  b: 3
}

console.log(hello);
({a, b} = hello);
console.log(a);

In this experiment i just added a console.log(hello); and now de-structuring works fine.

So there is two question

In example #1, why it's saying that hello is not declared, as it is declared right before de-structuring ?
In example #2, why it's working just adding console.log(hello) before de-structuring ?

asked Mar 31 '20 at 16:20

Ratul Sharker

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1. The parens are trying to call a function, which happens before a value is assigned to `hello`. 2. You put a semi-colon after `console.log`. – Quentin Mar 31 '20 at 16:23
De-structuring syntax causes function call i didn't know that. @Quentin Thanks for that. Could you please let me know more which function is actually called, it has no name specified. – Ratul Sharker Mar 31 '20 at 16:47
1

It's trying to call the object literal as a function. `({a: 1, b: 3}());` – Quentin Mar 31 '20 at 16:51
Now i get it properly. +1 @Quentin – Ratul Sharker Mar 31 '20 at 16:53
Add a semicolon after the closing parenthesis of hello object declaration. It'll prevent the next expression from turning into a function call – Adarsh Hegde Mar 31 '20 at 16:57
Yes i got this, thanks @AdarshHegde – Ratul Sharker Mar 31 '20 at 17:11

Why javascript object de-structuring is not working?

0 Answers0