This article summarizes how to specify brackets and variables for variable properties in Javascript.

Conclusion

const key = "variable"
object[key]

object["categories[]"]

How to Use Variables in Object Properties

Normally, when accessing data from an object like this,

object: {
  key: "This is the key"
}

It is used like this,

object.key // This is the key

However, there are times when you want to dynamically use a variable as a property.

Solution

const variable = "key"
object[variable] // This is the key

This way, you can use a variable.

How to Use an Array (Square Brackets) in Object Properties

Sometimes you may want to specify something like

object.category[]

such as when using URL parameters.

However, this will result in a syntactic error.

Solution

Just like with variables before, you can do the following:

object["category[]"]

Summary

I have written about the syntax for using variables and square brackets in Javascript object properties.

I hope this can be helpful to someone.

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That's it!