Javascript Destructuring

Question

var obj = {id: 42, name: "Jack"};

let {id = 10, age = 20} = obj;

console.log(id); // 42
console.log(age); // 20

why does the id output is 42 and not 10.Doesn't the let makes the second id value assigned override the old value which is 42 and thus takes a new value which is 10?

Answer 1

It's default parameter, used when the key is not contained in the destructured object.

For age, because the key isn't contained in obj, so the default parameter effect.

For id, because the key already exists, the default parameter is disregarded and the value in obj is extracted.

Answer 2

• How to Use Object Destructuring in JavaScript — https://dmitripavlutin.com/javascript-object-destructuring/

Answer 3

You can set a default value if the property doesn’t exist in the destructured object.

Answer 4

the equal sign changes the values
first id = 42, then the id = 10 and lastly
{id = 10} = {id = 42} therefor the last value of the id is 42;
In short the last value to be passed is true😍😍