Understanding the Main Use of 'Symbol' in ES6

The JavaScript ES6, also known as ECMAScript 2015, introduced a new primitive data type known as 'Symbol'. A Symbol is fundamentally used to create unique, immutable identifiers. This aspect separates them from primitive data types like number, string, and boolean.

The primary purpose of a Symbol in ES6 is to generate a unique identifier that helps in property naming, preventing property name collisions. This aspect is immensely useful in situations where you don't want certain properties on an object to be overwritten or manipulated.

Practical Application of Symbol in ES6

Consider a scenario where you have an object with properties in a library. You want to add some more properties to the object without worrying about your new property names clashing with the existing ones. This is where the Symbol data type comes into play.

Here is an example:

let uniqueSym = Symbol("mySymbol");
let obj = {
    [uniqueSym]: "Hello ES6"
};
console.log(obj[uniqueSym]); // Outputs: Hello ES6

In the above example, uniqueSym is a Symbol that creates a unique, non-enumerable property for the obj object. The property can't be overwritten or accessed mistakenly because it's hidden and used internally within the object.

Best Practices

While using Symbols in JavaScript, following best practices ensures robust and error-free code:

• It is advisable to give each Symbol a human-readable description. This doesn't affect the uniqueness of the Symbol but improves code readability.
• Unlike other JavaScript primitives, two Symbols cannot be compared or are not equivalent, even if they have the same description. So, be careful while comparing Symbols.
• The most common use case of Symbols is to create private object members, so make sure you don't expose these members unintentionally.
• The Global Symbol registry should be used sparingly as it introduces a global state into the application.

In conclusion, ES6 Symbols are a powerful way to create unique, immutable identifiers preventing name collisions and enhancing the robustness of your JavaScript code. They provide a stronghold for creating private properties and a method to prevent accidental property name collisions.