When and Why Use Square Brackets in Object Literal Property Names?

Understanding Brackets in Object Literal Property Names

In JavaScript, object literals are commonly used to represent data as key-value pairs. However, a less familiar syntax involves square brackets surrounding property names. Let's explore the significance of this syntax.

Computed Property Names

Introduced in ES6, square brackets allow for the creation of computed property names. Unlike traditional property names that are static strings, computed property names can be dynamic expressions, evaluated at runtime.

Example:

dist: {
    files: {
      [bpr + 'lib/Monster.min.js']: ['<%= concat.dist.dest %>']
    }
  }
}

In this example, the property name is dynamically generated using the expression bpr 'lib/Monster.min.js'. This feature enables you to define property names based on dynamic variables or other computations.

Use Cases

Computed property names are particularly useful when:

• You want to create dynamic property names based on user input or external data.
• You need to access properties of an object using variables or expressions.
• You want to avoid using string concatenation to create property names.

MDN Definition

The Mozilla Developer Network (MDN) defines computed property names as:

"Starting with ECMAScript 2015, the object initializer syntax also supports computed property names. That allows you to put an expression in brackets [], that will be computed as the property name."

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