在 JavaScript 中定义 enums 的首选语法是什么？

Question

What is the preferred syntax for defining enums in JavaScript? Something like:

my.namespace.ColorEnum = {
    RED : 0,
    GREEN : 1,
    BLUE : 2
}

// later on

if(currentColor == my.namespace.ColorEnum.RED) {
   // whatever
}

Or is there a more preferable idiom?

转载于:https://stackoverflow.com/questions/287903/what-is-the-preferred-syntax-for-defining-enums-in-javascript

Answer 1

Since 1.8.5 it's possible to seal and freeze the object, so define the above as:

var DaysEnum = Object.freeze({"monday":1, "tuesday":2, "wednesday":3, ...})

or

var DaysEnum = {"monday":1, "tuesday":2, "wednesday":3, ...}
Object.freeze(DaysEnum)

and voila! JS enums.

However, this doesn't prevent you from assigning an undesired value to a variable, which is often the main goal of enums:

let day = DaysEnum.tuesday
day = 298832342 // goes through without any errors

One way to ensure a stronger degree of type safety (with enums or otherwise) is to use a tool like TypeScript or Flow.

Source

Quotes aren't needed but I kept them for consistency.