Why Does Object Destructuring Require `var`, `let`, or `const`, But Array Destructuring Doesn't?

Object Destructuring without var, let or const

In JavaScript, object destructuring can fail with a SyntaxError if it's not properly declared.

{a, b} = {a: 1, b: 2};

This error occurs because the {...} operator has multiple meanings. When it appears at the beginning of a statement, it represents a block, which can't be assigned to. To resolve this issue, you need to explicitly declare the variable using var, let, or const:

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

Bonus Question: Why Don't We Need a var for Array Destructuring?

Unlike object destructuring, array destructuring doesn't require a declaration because it doesn't involve creating new variables. Instead, it re assigns values to existing variables in the scope.

[c, d] = [1, 2];

Here, [c, d] is an expression that reassigns the values of the array [1, 2] to the variables c and d.

In Summary

Object destructuring requires a declaration (var, let, or const) if it's not part of a block statement to disambiguate it from block syntax. Array destructuring, on the other hand, doesn't require a declaration since it reassigns values to existing variables.

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