Evolving Perspectives on TypeScript and JavaScript Integration

In this Hasty Treat, Scott and Wes talk about enums in JS — what they are, what they do, and how they work in JavaScript.

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03:11 - What are enums?

• A type restricting variables to one value from a predefined set of constants
• Direction = UP / DOWN / LEFT / RIGHT
• Role = ADMIN EDITOR AUTHOR VIEWER
• Day of the Week

05:12 - In GraphQL

• enum Role { ADMIN EDITOR AUTHOR VIEWER}
• Then

07:05 - In TypeScript

• First, declare the type:
  • enum direction = { UP, DOWN, LEFT, RIGHT }
• Then when you defined your function, use that type
  • type User { role: Role } or type User { role: [Role] }

08:49 - In JavaScript

• Not in JS yet
• There is a proposal in stage 1
  • https://github.com/rbuckton/proposal-enum
• And a babel plugin:
  • https://www.npmjs.com/package/babel-plugin-const-enum
• Can use case/switch
• Can use Object or Map keys

• Syntax 287: Hasty Treat - Records and Tuples in JavaScript

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