What is Bracket Notation and How Can It Be Used in Object Literal Keys in JavaScript?

Understanding Bracket Notation in Object Literal Keys

JavaScript offers a versatile syntax for defining object literals, including the usage of square brackets [ (…) ] in key positions. This syntax enables the dynamic specification of object properties based on computed values.

Consider the following example:

<code class="javascript">let a = "b"
let c = {[a]: "d"}

console.log(c)  // Object {b: "d"}</code>

This code assigns the property "b" to the object c, where the property name is computed based on the value of the variable a. It behaves identically to the following code:

<code class="javascript">let a = "b"
let c = {}
c[a] = "d"</code>

In ES2015 (ES6), this computed property name syntax was introduced as a convenient way to dynamically generate object keys. It is syntactic sugar for the equivalent property assignment using brackets:

<code class="javascript">c["b"] = "d"</code>

This syntax is particularly useful for working with dynamic or complex keys, such as those generated from user input or computed during runtime. It enhances code readability and simplifies property assignment, especially when dealing with object keys that may not be known in advance.

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